Riders Of Vision

General => TechTalk => Topic started by: The Prophet of Doom on November 15, 2013, 02:27:35 AM

Title: Shimming Woes
Post by: The Prophet of Doom on November 15, 2013, 02:27:35 AM
Time to do shims which I've not done before.
Armed with the instructions, shim tool and feeler gauge I set to it.
Measuring went OK, except 2 sets of feeler gauges disagree with each other which is annoying more than anything.

Think I've got everything right with the shim tool dot mark lined up with EX then rotate anti-clockwise
It rotated till the end of the shim tool just peeked around the bottom tail sticking straight up, (seems dead in the centre of the buckets) and rotating stopped.  the buckets have not depressed and theres no way to get the shims out - they only have a tiny bit of movement. 

I thought I was being too gentle so leaned on it a little bit. Now the whole thing is locked up and the flywheel bolt is spinning off if I try to go further anticlockwise.

Any ideas where I went wrong and what the hell do I do now? Remove the cams?
Title: Re: Shimming Woes
Post by: Rikugun on November 15, 2013, 07:50:31 AM
It appears the tool's ramp is not engaging the buckets sufficiently to depress them. In order for that to happen, rotation would need to continue but the long tail appears to be hitting the head stopping any further rotation in that direction. On that particular one, I'd install the tool from the other side and spin the cam in the opposite direction. The tool I've got appears to have two reference marks, does yours?

As I recall there is one position per head that requires attacking from the opposite side due to a casting that interferes with rotation relative to the other position on the same cam. I'm not sure if that's the case here but worth noting. It might be easier to ignore the manual instructions and visualize on a case by case basis where the tool needs to be positioned to depress the buckets sufficiently while remaining aware of any rotational obstructions, lobe position and of course leaving room to work and extract the shims. Easy, right?   ;)

I'm not sure if it's just the picture angle but it also appears the tool is engaging only one bucket. It sometimes takes a few tries to get it nestled in there correctly and only a subtle shift makes all the difference. I'd back the cam off in the other direction to extract the tool and try it from the other side.
Title: Re: Shimming Woes
Post by: Re-Vision on November 15, 2013, 09:01:05 AM
Before the Postal Service stole my shims and tool, I familiarized myself with them and I believe Gary is correct in everything he said. Insert the tool from the other side and make sure the tool depresses both buckets. Should be a smooth operation.    BDC
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 15, 2013, 04:07:44 PM
Thanks guys. 
Currently the tool is jammed in there.  Any idea how to get it out?
Title: Re: Shimming Woes
Post by: Re-Vision on November 15, 2013, 04:43:11 PM
I suspect your tool is wedged in, try rotating the engine while applying force to unwedge the tool.    BDC
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 16, 2013, 05:33:49 AM
I'll try that tomorrow.  If it's totally wedged in there I'll have to loosen off the cam I think.  Grrrr

I hope you managed to get compensation from the Post Office.  Makes me nervous about lending my tool via post, but we can't be too precious about things I guess.  At least they are still available.
Title: Re: Shimming Woes
Post by: Re-Vision on November 16, 2013, 06:27:39 AM
I'll bet if you pry up on the tool while rotating the cam, it will come out. Don't ship shims with your tool, they think they are stealing coins.     BDC
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 17, 2013, 04:38:38 AM
You bet correctly, the tool is free,  Whew!  Thanks Bobby.
Six years on RoV and I don't recall ever reading that the instructions for shimming are incorrect

Looks like the cam timing on the rear cylinder is out though so I'll need to jiggle around with that.
Title: Re: Shimming Woes
Post by: Re-Vision on November 17, 2013, 06:52:57 AM
Your tool doesn't look the same as mine did, is it an official Yamaha Vision tool?    BDC   
Title: Re: Shimming Woes
Post by: Rikugun on November 17, 2013, 08:34:12 AM
When I read you'd managed to loosen the flywheel bolt I figured you really got after it! Glad to hear you got the tool free.  :)

How far off is the timing - half a tooth? one tooth? Can you get a pic showing it? Does it look like chain stretch or has someone been in there before you?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 17, 2013, 08:19:49 PM
Quote from: Re-Vision on November 17, 2013, 06:52:57 AM
Your tool doesn't look the same as mine did, is it an official Yamaha Vision tool?    BDC   
Yes it's a genuine Yamaha - direct from the dealer with a Yamaha part number sticker and everything.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 17, 2013, 08:35:02 PM
Quote from: Rikugun on November 17, 2013, 08:34:12 AM
When I read you'd managed to loosen the flywheel bolt I figured you really got after it! Glad to hear you got the tool free.  :)

How far off is the timing - half a tooth? one tooth? Can you get a pic showing it? Does it look like chain stretch or has someone been in there before you?
Has someone been in there before me? Hell yes.  Half of what I do to this bike is undoing the shit work that the PO did, and interestingly he was a professional mechanic and spray painter - all I can say is I feel sorry for his customers.  For example he sprayed the tank ON THE BIKE! and didn't even bother masking the frame much.  Wrong screws everywhere, wires just twisted together with a bit of tape, extensive use of GLUE.  I could go on and on...

When the front is at the T mark, the cams registrations look perfectly aligned to the marks on the clamp (Pic 1)
When the rear is at 2T mark (Pic 2) the intake looks about 1.2 a tooth out to the left (Pic3),  exhaust looks about 1/2 a tooth out to the right (Pic 4)
Title: Re: Shimming Woes
Post by: Rikugun on November 18, 2013, 12:50:07 PM
Hmm, that does look a little off.... :(  It will be interesting to see if it runs differently once corrected.

Regarding tools - a pic of mine below and a link to another tappet tool discussion:
http://ridersofvision.net/rovforum/index.php?topic=1882.0 (http://ridersofvision.net/rovforum/index.php?topic=1882.0)
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 18, 2013, 05:29:11 PM
Not entirely sure of the procedure for this - I presume I undo the tensioners first?
I'm thinking I need to move a tooth on the bottom by dropping the chain a bit and lifting it up, then fit the cams in place exhaust, then intake so the marks line up?
Title: Re: Shimming Woes
Post by: cvincer on November 18, 2013, 07:43:41 PM
I removed the chain guide ,    removed the tensioner   & found I had enough play in the chain to (with a bit of wiggling) turn the cam & re-locate the sprocket tooth into the next chain link; remember the chain between both sprockets  must be tight .  I then stuck my finger in the chain tensioner hole to tighten up the chain & ensure that the punch marks on both cam sprockets were lined up with the index marks on their cam clamps.       When you have got the cam where you want it, & have replaced the chain tensioner (remember to push its shaft in hard against the the chain) ,  turn over the engine by hand (socket on the flywheel bolt) several times to check your adjustment has not resulted in the piston hitting a valve.    A compression test before & after adjustment might be a good idea.

You talk about moving the chain around 1 link on the bottom cog (deep inside the engine) ........ using a spare engine with its
cylinder heads removed I tried this ...... it's not possible.    I reckon the engine would have to be completely stripped to do it.

.


Title: Re: Shimming Woes
Post by: fret not on November 18, 2013, 08:31:37 PM
You have to move the chain on the cams.  After all, THEY are what you are trying to get in synch with the crank.  Crank and piston position are what you use for reference for setting other things like timing and valve clearance adjustment.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on November 18, 2013, 11:16:12 PM
Thanks for the feedback guys, but I don't get it.
If you look at the pics above, when the flywheel timing mark is dead on, then both cams are what looks like 1/2 a tooth out.  How can I move a cam half a tooth?
Title: Re: Shimming Woes
Post by: fret not on November 18, 2013, 11:49:26 PM
Is the cam chain tensioner in place?  Adjusted?  Any slop in the chain can allow significant error in the reading.
Title: Re: Shimming Woes
Post by: Rikugun on November 19, 2013, 08:00:11 AM
Is the cylinder the tappet tool got stuck in the same that the timing is off? If yes, was the timing off prior to getting the tool stuck and subsequently free? Have you tried turning the engine over in it's normal direction a few rotations and re-check the cam timing marks?

If you rotate the engine against it's normal direction how much delay is there before the cams turn and is the delay the same front and rear cylinder?

Quote from: ProphetOfDoom on November 17, 2013, 08:35:02 PM
... the intake looks about 1.2 a tooth out to the left ...

When first I read this I wondered how you measured so accurately - one point two teeth... After looking at my keyboard I realize it was a typo.  ;D  ;D 1/2 tooth isn't so bad  LOL

Title: Re: Shimming Woes
Post by: pinholenz on December 09, 2013, 12:34:20 AM
Hi Rohan, you will guess that I have more than a passing interest in this! How has the issue unfolded?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 09, 2013, 01:16:52 AM
On hold while I get some transport together.  ETA about a week ago.
Last I touched it I'd moved something and now hitting the piston on a valve I think.
Title: Re: Shimming Woes
Post by: pinholenz on December 09, 2013, 04:30:16 AM
So that was one of your old xz400's that you bought back?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 09, 2013, 08:02:45 AM
Yes,
More through coincidence than anything - Since I sold it it's turned into a bit of a lemon
Title: Re: Shimming Woes
Post by: Rikugun on December 09, 2013, 09:42:40 PM
Quote from: ProphetOfDoom on December 09, 2013, 01:16:52 AM
On hold while I get some transport together.  ETA about a week ago.
Last I touched it I'd moved something and now hitting the piston on a valve I think.
I've warned you about "touching it" yourself.  This is what happens...   :laugh:  :laugh:

Seriously though, what did you do??
Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 10, 2013, 01:43:32 AM
Quote from: Rikugun on December 09, 2013, 09:42:40 PM
Seriously though, what did you do??
Don't know what I did to cause it, but I've stopped looking at it till I get the other bastard bike going.
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 10, 2013, 01:57:55 AM
I know I'm a bit late to the show here, but I think maybe I can offer some help, POD.

I recently did a cylinder disassembly/rebuild a total of five times, and I found the same thing that your photos show. As ridiculous as it sounds, it appears that for my bike it is possible for the alignment of the camshafts to be off half a tooth or so without disrupting the free turning of the engine. However, if the camshafts are aligned properly then the engine will turn over much more smoothly and quickly. In getting them aligned properly, this is what worked for me. YMMV, I suppose.

With sprocket and cam setting, we have three marks to align- the dot on the sprocket, the line on the bracket holding the cam down (it's the wedge-shaped line on the side of the bracket), and there's a hole in the end of the camshaft that is drilled into the round part of the shaft that can be seen between the sprocket and bracket when looking down onto the head from above. (See photo here)

(http://i1279.photobucket.com/albums/y537/aphexapex/cam_zps649881ed.png) (http://s1279.photobucket.com/user/aphexapex/media/cam_zps649881ed.png.html)

Obviously, the idea is that this "camshaft hole" is going to be lined up perfectly with the mark on the sprocket whenever the sprocket is locked properly onto the little dowel pin on the end of the camshaft (and then afterward the sprocket and camshaft can be turned together to line up with the line on the bracket). In actuality, the camshaft hole can be moved slightly to the right or left of the line on the bracket while the sprocket remains in the same position relative to the chain. In other words, the tooth of the sprocket wiggles inside the chain link for a measure of about "half a tooth". If both sprockets are wiggled in the same direction, you can set one of them off a total of one tooth, and your timing marks will look correctly aligned.

Ignore the mark on the sprocket. You want to base your timing here off the alignment of the camshaft hole and the line on the bracket. If those two are in line with each other, then place your sprocket onto the camshaft with the dowel pin in the correct slot (Haynes will explain this). Do this with the sprocket furthest from the chain tensioner first. Have the chain placed onto the sprocket before placing the sprocket onto the cam, and see that the chain from sprocket down into crankcase is as taut as possible while still allowing the sprocket to fit onto the cam with ease. This part is very important- you are setting one sprocket as close as possible to the proper alignment, while leaving yourself plenty of room to play around with the other sprocket until you find the sweet spot of smooth revolution.

Once the sprocket furthest from the chain tensioner has been placed with the chain onto the camshaft, put the sprocket bolt on hand-tight. This next part is tricky and if you accidentally knock the sprocket off the camshaft you could lose that little dowel pin down in the crankcase (I did this, it was a blast. Called over friends and had a party.)

What I discovered here is this: You can rotate a camshaft the distance of "half a tooth" to the left or right and not see a noticeable difference in the alignment of camshaft hole and line on bracket. Do this with both sprockets and you have a total of one tooth off. At this point the engine will turn without locking, but it will be stiff and slow. This is how I found my settings when I first got into my cylinders.

Now that the first sprocket is placed onto the cam with the chain in proper place around it, rotate your other cam so the camshaft hole is lined up with the line on the bracket. Take the sprocket for that cam and place the chain over it so that the tension of the chain between the two sprockets is so tight that you can just barely work the sprocket onto the cam. The sprocket should be a tight squeeze going onto the cam, but then chain tension between the sprockets should loosen a little once the second sprocket slides on. If tension doesn't loosen up when second sprocket is placed on, the the second sprocket needs to be moved down the chain by one tooth.

Put on the bolt on the second sprocket, hand tight, then stick your fingers through the chain tensioner hole and push out the slack in the chain, and turn the engine over counter-clockwise. It should turn very smoothly and with hardly any real effort. If it turns slowly or with a lot of drag, then either your sprocket closest to the tensioner needs to be turned counter-clockwise by one more tooth, or your tension between the other sprocket and the lower crankcase is one tooth too tight.

I hope this all makes some kind of sense. I encountered settings that looked identical to what your photos show, and it took a great deal of experimentation to find out that it's possible for your camshaft timing to be slightly off and still allow for full continuous revolution of crankcase. When you get them lined up perfectly, the difference in ease of rotation is immediately evident even though it only looks like a slight difference with the timing marks.
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 10, 2013, 02:34:50 AM
Ok, that sounds way too confusing.  :-[

What I'm trying to say is that when it comes to lining up your marks,

1. Go by the camshaft holes, NOT the marks on the sprockets

                                        and
 
2. Both cams have a little bit of wiggle room while still allowing the engine to turn. There is not just one setting that will allow free revolution of the engine, but actually two.

       So...

Set the sprocket furthest from the chain tensioner so that the chain between it and the lower crankcase is as tight as possible, then set the sprocket closest to the tensioner so that the chain between the sprockets is as tight as possible. Test your revolutions by putting your fingers into the tensioner hole and pushing on the chain, and make all your adjustments on the sprocket closest to tensioner.

I wouldn't allow the chain to move around down inside the crankcase...that stuff is already set and you can make all your necessary adjustments from up top.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 10, 2013, 03:26:00 AM
Awesome, thanks for the long description Fuzzle.  So far I've been leaving the sprockets bolted on the cam.  Didn't even know about the hole.

Yes I'll take care of the pin.  When I did a practice on my spare engine I dropped one of those plastic oil caps down the chain tunnel - being plastic there's no fishing them out without surgical endoscope equipment
Title: Re: Shimming Woes
Post by: QBS on December 10, 2013, 10:34:16 AM
Fuzz, thank you for all the effort you put into the above epistle.  Truly a labor of brotherly love.  Well done.
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 10, 2013, 05:51:33 PM
ROV has helped me immensely and if there is anything I can do to return the favor then I'm more than happy to.  :)

I think it is possible to move the chain around without removing the sprockets, but for me it was easier to get a feel for proper chain tension by pulling the sprockets off and testing one position, pull off and try another, etc.

Once you land on the perfect alignment you'll know immediately. The engine can be turned in both directions with great ease.

I would also suggest turning the engine over for several revolutions before closing everything back up. If alignment is off and the engine is going to lock, it may take more than three or four revolutions to do so (I can't remember the exact number).

Just as a guess, I would say from the looks of your photos that the sprocket on the rear intake needs to be turned one tooth clockwise, while the exhaust remains as is.
Title: Re: Shimming Woes
Post by: pinholenz on December 10, 2013, 07:16:26 PM
Hi Fuzzlwump,

For those of us anticipating doing our shims, while we have got the covers off, is easy turning of the engine in both directions a sure test that the chain and cams are properly lined up?. In other words, if the engine turns over sweet and smoothly in both directions using the flywheel nut, its all OK. It aint broke, don't touch the cam sprockets or chains!!?
Title: Re: Shimming Woes
Post by: Rikugun on December 11, 2013, 07:26:22 AM
I'm a little puzzled why cam timing being slightly off (without causing piston interference) would have such a dramatic affect on ease of engine rotation. Any theories?
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 12, 2013, 11:07:30 PM
Quote from: pinholenz on December 10, 2013, 07:16:26 PM
For those of us anticipating doing our shims, while we have got the covers off, is easy turning of the engine in both directions a sure test that the chain and cams are properly lined up?. In other words, if the engine turns over sweet and smoothly in both directions using the flywheel nut, its all OK. It aint broke, don't touch the cam sprockets or chains!!?

If my understanding is correct, and if my experience is not unique, then yes, everything should be OK as long as you get free turning of the engine. But I wanna be honest and say that I'm still new to this stuff and there is a lot I haven't learned yet. So this is just my experience...I can't suggest that it be taken as gospel.

Haynes manual says that when installing the cams and sprockets, you should check your work by turning the engine counter-clockwise to make sure that the engine doesn't lock up. It does not explain why you should go counter-clockwise, so I tried turning in both directions and found the turning to be smooth in both directions once  I had the timing set correctly. I didn't have the engine mounted into the driveshaft, and I don't know if that would somehow make a difference.

Haynes mentions turning the flywheel nut for two or three revolutions, but I discovered this is not an adequate number of turns to determine for sure that you won't get lock up. I turned it over two or three times, put the engine back on the bike and had it all back together, pushed the starter....locked up. Had to take everything back apart. When I had everything done over, I turned for a count of about thirty seconds...totally unnecessary, but I had some paranoia to get rid of! lol

I didn't do the shims with the cams still in place because I had everything apart already. I don't know about the difficulty of doing it that way, but I can vouch that Rikugun is correct when he mentioned that you have to be careful how you position your wrench when holding the cams with it. The way the heads are cast, it is very easy to accidentally hit and mar the mating surface for the head cover gaskets if you don't hold your wrench just so.

Quote from: Rikugun on December 11, 2013, 07:26:22 AM
I'm a little puzzled why cam timing being slightly off (without causing piston interference) would have such a dramatic affect on ease of engine rotation. Any theories?

Man, this is a very good question. When I was doing this work I couldn't make any sense of it...it simply doesn't add up when you consider the basics of how the engine works, so I'm still wracking my brain over it...
Title: Re: Shimming Woes
Post by: Rikugun on December 13, 2013, 09:39:54 AM
QuoteHaynes manual says that when installing the cams and sprockets, you should check your work by turning the engine counter-clockwise to make sure that the engine doesn't lock up. It does not explain why you should go counter-clockwise
When possible you should turn the engine CCW because that is it's normal direction. To do the valve lash you must turn opposite at times to accommodate the bucket tool but otherwise you turn an engine (especially OHC) over in the direction it runs. It's less stressful on the auto chain tensioners for one reason. 

I would think 2-3 full crank revolutions would do it. From wherever you start it takes 2 full crank revs to rotate the cams once since they spin at half crank speed. When you took it apart again what did you find was the reason it locked up?  Were the tensioners in place when you test spun the motor? Did you spin it fully twice CCW?

Title: Re: Shimming Woes
Post by: Fuzzlewump on December 15, 2013, 06:58:45 PM
The first go around, my timing was off and piston met valves, locking everything up. It appeared that when testing the timing by cranking over the engine, I had turned the crank all the way up to locking point and then stopped just before the engine locked. Once everything was put back together, I pushed the start button and there was no cranking before lockup, just immediate lockup.

Tearing it all apart, I reset cam timing and this time turned the crank several times until I was satisfied there was no lockup. This was done with the chain tensioner in place, as well as the chain guard on the other side. It turned without locking, but was stiff and not smooth. It felt as though compression would build up to so great a degree that I could only barely crank it by hand,  then the exhaust valves would open and rotation was easy again.

I changed the timing by one tooth, did the above test again and this time had a crank that felt strong but smooth, more evenly balanced between compression buildup and release. It puzzled me that there could be two timing settings that would allow free revolution of the engine, this just didn't make sense. My understanding was that there was simply only one proper setting for the timing. So I changed the timing back to the way it was, and then back again. After playing around with it for a while I verified for myself that there are in fact two settings. Because one feels "unbalanced" and the other feels smooth and sweet, I chalked it up to another Vision flaw.

Thinking about it some more, I have only one theory on how this is possible. If the timing is off by one tooth, then the engine should not be able to spin freely- there will be piston/valve contact. I think that on this engine this is not the case...if you are off by only one tooth, the timing of compression buildup and release is maladjusted just enough to create an early buildup and late release, but not enough to cause piston/valve contact. When I felt resistance in cranking, it felt like too much compression followed by violent release. My understanding of 4-stroke intake/exhaust timing is still very limited,  so I'm going with a guess here. All I can say really is what I experienced, and unfortunately not how it could plausibly be.


Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 15, 2013, 09:12:08 PM
Thanks for your notes Fuzzlewump, since I have this to do on 2 bikes now it will help a lot
Title: Re: Shimming Woes
Post by: QBS on December 15, 2013, 10:28:03 PM
So Fuzz, you did all your crank turning experimentation with the spark plugs installed?
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 15, 2013, 11:58:18 PM
Quote from: QBS on December 15, 2013, 10:28:03 PM
So Fuzz, you did all your crank turning experimentation with the spark plugs installed?

Oh no, I wasn't able to turn the engine over with the plugs installed, too much compression to do by hand.

What I mean is that the resistance/release that I found in turning the crank felt like compression buildup. It didn't feel related to chain tension or locked gears....it was "soft", for lack of a better word.

I took this to mean that even with the spark plugs removed there is a certain small amount of compression that will be built up until the piston has pushed all the air out. Like an inflated tire with a hole punched into it...pressure is built up in the tire but that amount of pressure is steadily decreasing as the total volume of air reduces by leaking out of the puncture.

My understanding is that even when you crank the engine by hand, the piston moves quickly enough to compress some air before it all leaks out the spark plug hole....is this incorrect? Now I'm confusing myself, lmao!
Title: Re: Shimming Woes
Post by: Rikugun on December 16, 2013, 12:00:04 PM
I would caution against the notion of gaging correct cam timing by ease of crank rotation. This is going to be highly subjective and non-scientific.  :) There are probably several timing changes that don't result in piston interference but do result in more or less crank rotation resistance. Only one however is the correct factory setting!  :) That's not to say you can't experiment with different settings to (for instance) move the torque curve up and down the rev scale but I'd suggest using a degree wheel for that. More than a basic understanding of 4 stroke theory would help here too.  :)

About the crank rotation resistance - besides "phantom" compression effects another ex[lanation may be relative position of the cam lobes from both cylinders. Depending on their sequencing and how many are approaching, climbing, or fully on the lobe, resistance will change. It's not compression necessarily but the effort to move say two valve springs vs. one at a time and where they are on the ramp.

If the engine has not been apart before it's a good practice to carefully note position of timing marks prior to disassembly. Even then you want to carefully follow manual instructions during assembly. If confidence in the current cam timing is low (i.e. PO's failed attempt) follow the instructions carefully noting crank position, which side of the chain needs to be taught, sprocket index marks etc. and you'll be rewarded with success.  Just my 2 cents. :D

EDIT: re manual instructions... I think Fuzzle referenced the Haynes manual but wasn't there a discussion not long ago where some discrepancies were found in the Yamaha manual in the cam timing section?
Title: Re: Shimming Woes
Post by: QBS on December 16, 2013, 12:07:40 PM
The spark plug hole is pretty big.  It's not going to provide much compression resistance to hand cranking rpm.  I think that gathering data and drawing conclusions  from it, by turning the crank opposite of the engines' designed rotational direction is a bad plan that may lead you down erroneous rabbit holes.  Get the crank to turn freely and easily when rotated in the correct direction and go forward from there.  Also, don't discount the crankshaft rotational resistance induced by the operation of the valve train.
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 16, 2013, 02:18:49 PM
Very informative and insightful, guys...this takes a lot of puzzlement out of my experiences with the cam timing. Thank you!

As an added thought, what problems could possibly arise from rotating the engine in the reverse direction when testing cams? Rikugun mentioned added stress on the chain tensioner...are there any other things that might arise from this?

I ask because I've been having some strange issues regarding coolant leaks that appear to be related to rpms of engine. Could I have stressed a component of the crankcase that is now heating faster than it should?
Title: Re: Shimming Woes
Post by: fret not on December 17, 2013, 01:22:59 AM
Coolant leaks are not related to the direction you turn the crank.

You should follow the shop manual directions for setting the cam timing and rotate the crank in only one direction to keep the cam chain taught on the side opposite the tensioner.  All the slop must be on the tensioner side, that is what the tensioner is there to control.  This is a precision system, so follow the manual for best results.
Title: Re: Shimming Woes
Post by: Rick G on December 20, 2013, 12:56:58 PM
Fuzz, there is a lot of machinery being turned when you rotate the crank. I see no advantage to turning it the wrong way.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on December 22, 2013, 07:18:51 AM
Quote from: Fuzzlewump on December 10, 2013, 01:57:55 AM
Ignore the mark on the sprocket. You want to base your timing here off the alignment of the camshaft hole and the line on the bracket.
I think this is the key - Using the marks on the sprocket I found that it was too easy to get it misaligned depending on whether your eye is off to one side, but think that it is right. 

Using the mark on the cam you can be sure everything is lined up perfectly.  I had no troubles doing it with the sprockets still on the cam

Thanks for the writeup Fuzzle
Title: Re: Shimming Woes
Post by: Fuzzlewump on December 23, 2013, 09:06:54 AM
You're welcome, Prophet, and thank you everyone else for correction and guidance on my post.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 01, 2014, 07:00:31 PM
Has anyone noticed that the angle of the cams is different front & rear? (back onto the 550 now)

Obviously on the front they both point in at TDC, and rear they both point out - that's because they are the other way around.  But the actual angle is different (front lobes stick up more at TDC) so the rear will push the valves down earlier in the cycle than the front.

My assumption would be that this makes one cylinder stronger at a particular rev range, and so broadening the power band to make it more rider friendly?

Any thoughts on this? Could judicious cam re-timing get a free HP boost over a tighter rev range?

BTW I'm also inverting one cylinders cams 180 degrees (aka twingle, twumper, big-bang, close firing V)
Title: Re: Shimming Woes
Post by: fret not on January 01, 2014, 11:50:28 PM
That should be interesting, I hope you report to us when you run the bike.  I'm curious as to the effect on fuel consumption, if any, and smoothness/vibration.
Title: Re: Shimming Woes
Post by: Rikugun on January 02, 2014, 01:18:28 PM
Quote from: ProphetOfDoom on January 01, 2014, 07:00:31 PM
Has anyone noticed that the angle of the cams is different front & rear? ... the actual angle is different (front lobes stick up more at TDC) so the rear will push the valves down earlier in the cycle than the front.

Hmmm.... I have not noticed that. I'm surprised (and a little skeptical!) they are different but I'll certainly take note next valve lash check. Are you sure it doesn't just look that way as a result of asymmetrical lobes, valve angle, tequila consumption, etc?

Very curious to learn what the power delivery/engine pulses are like when "twingle timed".  ;D
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 04, 2014, 03:03:40 PM
Quote from: Rikugun on January 02, 2014, 01:18:28 PM
Hmmm.... I have not noticed that. I'm surprised (and a little skeptical!) they are different but I'll certainly take note next valve lash check. Are you sure it doesn't just look that way as a result of asymmetrical lobes, valve angle, tequila consumption, etc?
No need to be skeptical Rikugun, just look at the picture of the Cam sprockets.  See how much narrower the alignment angle is on Front as opposed to Rear (the alignment slots on the bottom of the sprocket.
Since the alignment pin is in line with the lobes this makes for a much flatter angle on the rears - or am I missing something?
Title: Re: Shimming Woes
Post by: Rikugun on January 04, 2014, 08:12:43 PM
Don't ask me, I've never even had the head off one of these things....   :P  :)
Title: Re: Shimming Woes
Post by: Rikugun on January 22, 2014, 10:01:21 PM
Where did you get the cam alignment picture and do have one of the rear?

Did the different cam timing play into the decision to twingle one cylinder over the other and why?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 23, 2014, 03:55:59 AM
It came out of one of the service manuals, but don't recall which.  Heres another one which shows the difference.  It doesn't show the lobe, but the pin hole on the cam is aligned with the lobe, the cams are same front & rear.

No it didn't make a difference for twingling I did the rear because it was physically more accessible and because I realised (thanks to your earlier post) that there is no difference front and rear in terms of timing in relation to the crankshaft and the other piston.

However.....
That's a different subject than the lobe separation angle (LSA) front & rear.  My reading would suggest that it helps engine designers select power characteristics















Tighter LSAWider LSA
Moves Torque to Lower RPMRaise Torque to Higher RPM
Increases Maximum TorqueReduces Maximum Torque
Narrow Power bandBroadens Power Band
Builds Higher Cylinder PressureReduce Maximum Cylinder Pressure
Increase Chance of Engine KnockDecrease Chance of Engine Knock
Increase Cranking CompressionDecrease Cranking Compression
Increase Effective CompressionDecrease Effective Compression
Idle Vacuum is ReducedIdle Vacuum is Increased
Idle Quality SuffersIdle Quality Improves
Open Valve-Overlap IncreasesOpen Valve-Overlap Decreases
Closed Valve-Overlap IncreasesClosed Valve-Overlap Decreases
Natural EGR Effect IncreasesNatural EGR Effect is Reduced
Decreases Piston-to-Valve ClearanceIncreases Piston-to-Valve Clearance

Perhaps having them different contributes to the all-round nature of the bike, but by swapping round the sprocket on either front or rear cylinder the owner could tune the bike for characteristics they like.  This independent of the twingle mod.

Normally changing timing is a specialist job because go too far and you hit valves, blow up the engine etc, but we have two possible to settings we know work.  See that megacycle cam specs don't specify different lobe separation front & rear but they are 104/106 which is a tight angle.  So obviously megacycle have a different profile, but if you can't afford hot cams, this would be a free mod.

The only thing I don't understand is why the rear cylinder is jetted for more fuel.  On the basis of more fuel = more power I'd have thought jetting would be the other way round.

I'm just supposing about this stuff, but I do find it all very interesting and I have too much free time.  I hope I'm not boring everyone. I'd be interested what other people think.
Title: Re: Shimming Woes
Post by: Rikugun on January 23, 2014, 11:57:54 AM
Bear with me as I try to play catch and ask more potentially silly questions...   :)

Quote from: ProphetOfDoom on January 23, 2014, 03:55:59 AM
However.....
That's a different subject (twingling) than the lobe separation angle (LSA) front & rear.  My reading would suggest that it helps engine designers select power characteristics
Understood but never considered it as a scheme to select characteristics of an individual cylinder in a multi cylinder engine. Have you come across other bike engines where this is done? Is it more common then I imagined?

Perhaps having them different contributes to the all-round nature of the bike, but by swapping round the sprocket on either front or rear cylinder the owner could tune the bike for characteristics they like.  This independent of the twingle mod.
I wonder if some work was done along these lines (in addition to close firing) to the bike treedragon rode? He indicated the bike's owner was a bit tight lipped about the specifics either to protect secrets or enough time had elapsed such that the details were not fresh.

See that megacycle cam specs don't specify different lobe separation front & rear but they are 104/106 which is a tight angle. 
What do you mean by "tight" angle? Aren't those figures in the middle of the 98-112 usable range most engines use? Maybe they don't list lobe separation as it is function of sprocket orientation, not the grind as in a pushrod V8 cam.

The only thing I don't understand is why the rear cylinder is jetted for more fuel.  On the basis of more fuel = more power I'd have thought jetting would be the other way round.
I've seen the exhaust scheme blamed for different front/rear jetting - long front headers vs. short Y pipe rear. Also, more fuel doesn't always equate to more power. I realize this is akin to comparing apples and refrigerators but.... Some 2 stroke tuned exhausts require leaner jetting than stock. Better scavenging /efficiency allows more work to be done with less fuel. Stock jet sizes (or larger) may have it blubbering, "4-stroking" and fouling plugs.

I'm just supposing about this stuff, but I do find it all very interesting and I have too much free time.  I hope I'm not boring everyone. I'd be interested what other people think.
I find it interesting as well. Relative to the life of the forum I'm late to the party but don't recall seeing this brought up before. Have you found any references to this in the archives? Other than this Megacycle sheet, do you have any published data on the stock cams? Anyone who refers to the Vision as an "XV" is suspect. With the opening and closing data one could compute stock lobe centers for whatever that's worth.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 23, 2014, 04:26:51 PM
Quote from: Rikugun on January 23, 2014, 11:57:54 AM
Understood but never considered it as a scheme to select characteristics of an individual cylinder in a multi cylinder engine. Have you come across other bike engines where this is done? Is it more common then I imagined?

No, most of the stuff I found was about race cars.  They seem to blog a lot more than motorcycle guys, also it is generic information with the assumption that all cylinders are the same.  I've never heard of an engine that has different valve timing in different cylinders before.  I think that's quite unusual.
Theres a bit of chatter about how cosworth made the XZ a superbike and Yamaha de-tuned it for the popular market.  This would certainly be one way.  The big unknown would be how much low end is sacrificed for the top end increase and whether it's still usefully usable on the street.

Quote from: Rikugun on January 23, 2014, 11:57:54 AM
I wonder if some work was done along these lines (in addition to close firing) to the bike treedragon rode? He indicated the bike's owner was a bit tight lipped about the specifics either to protect secrets or enough time had elapsed such that the details were not fresh.
I have no idea.

Quote from: Rikugun on January 23, 2014, 11:57:54 AM
What do you mean by "tight" angle? Aren't those figures in the middle of the 98-112 usable range most engines use? Maybe they don't list lobe separation as it is function of sprocket orientation, not the grind as in a pushrod V8 cam.
Builders categorise lobe angle into tight and wide angle - tight meaning up to about 108o. But yes all within the range. 98-112 is not absolute.  Depending on piston cut-outs, compression even gasket you may be hitting metal on metal at the extremes which is why I think it's good that we have some options that are known to work well

Quote from: Rikugun on January 23, 2014, 11:57:54 AM
I've seen the exhaust scheme blamed for different front/rear jetting - long front headers vs. short Y pipe rear. Also, more fuel doesn't always equate to more power. I realize this is akin to comparing apples and refrigerators but.... Some 2 stroke tuned exhausts require leaner jetting than stock. Better scavenging /efficiency allows more work to be done with less fuel. Stock jet sizes (or larger) may have it blubbering, "4-stroking" and fouling plugs.
Yea, I've seen that also.  It doesn't necessarily make it so, but I'd agree that the super thin rear pipes can't be good for it.  My predators are larger, but treedragon used big pipe right from the head.  Exhaust mods are still in my mind, but not for this iteration I've spent enough already

Quote from: Rikugun on January 23, 2014, 11:57:54 AM
I find it interesting as well. Relative to the life of the forum I'm late to the party but don't recall seeing this brought up before. Have you found any references to this in the archives? Other than this Megacycle sheet, do you have any published data on the stock cams? Anyone who refers to the Vision as an "XV" is suspect. With the opening and closing data one could compute stock lobe centers for whatever that's worth.
No references I could find in the archive.  the cams are well documented in the service guides, except for timing, which is understandable as it's fixed by the pin.  Prcise timing can be easily worked out with a degree wheel (I have instructions on how to make one on your printer somewhere.

I don't think I'll progress this till after the build is running in twingled stock form, but it's good to think of things ahead of time and throw them out there.  The think I like about it is it would be a cheap and safe mod, whereas hot cams that need dremmeling clearance off the valve covers would be expensive and perhaps a bit more risky.
Title: Re: Shimming Woes
Post by: dingleberry on January 23, 2014, 07:05:45 PM
"The only thing I don't understand is why the rear cylinder is jetted for more fuel.  On the basis of more fuel = more power I'd have thought jetting would be the other way round."


Rear cylinders usually need more cooling and rich jetting is going to keep that combustion chamber cooler.
Probably has something to do with pre ignition/detonation as well but I'm not sure.
Title: Re: Shimming Woes
Post by: Rikugun on January 23, 2014, 10:34:50 PM
dingleberry - Generally I think of that in regard to air cooled engines but wouldn't summarily dismiss the idea for the XZ to some degree (see what I did there?) too.

POD - In the picture "cam sprocket" what are we looking at exactly? Is that supposed to be TDC compression for the front and rear cylinders viewed from the left?  EDIT: Fiatdoctors comments caused my brain to click into gear.. Some labels may be wrong but how about the inner sprocket orientation, marks and pins? Is that accurate and how yours looked when you timed it?
Title: Re: Shimming Woes
Post by: fiat-doctor on January 24, 2014, 07:22:39 AM
Not sure about all of this...   Keep in mind that I've not done this myself but look at the factory manual; the pictures and diagrams are just as you show BUT look at the ones that show the direction of chain travel...   they show the chains moving in opposite directions front and rear.
Both cylinders are at TDC on the compression stroke...  the next valve to open will be an exhaust valve.  If the cams are turning different directions on the  front and rear cylinders, the cam angle will need to be different because of the angle of the valves in the head.  One cylinders cam will be much further from the pair of ex valves and the sprocket compensates for this.  Look at the diagrams and see what you think.

If the cam love separation angle was being changed by the sprockets, the difference in the sprockets would be slight, not the huge visible difference that there actually is.

Just my take on it,
Steve
Title: Re: Shimming Woes
Post by: Rikugun on January 24, 2014, 10:41:30 AM
I'm obviously a little skeptical as noted by my initial accusation of tequila over-indulgence on the part of POD.  :) In that comment I also questioned if valve angle had been considered. Accepting that (like fiat-doctor) I haven't looked at the parts like POD has it's hard for me to "see" it. I've often wished I had my spare engine at home to play with and this one of those times.  :)

Looking at the "CAM SPROCKET" diagram above I forgot the front cam sprockets are viewed from the right whereas the rear are viewed from the left. The cams all spin CW viewed from the left but when setting front timing (from the right) they spin CCW. I mistakenly looked at the diagram as a literal representation of engine layout but is rather 2 diagrams viewed from opposite sides - duh.

At casual glance, and assuming the diagram is rendered accurately, the locating pin orientation looks very different - especially compared to the plane of the gasket surface. When valve angle and cam rotation are considered the differences appear less obvious. Does this make sense or am I (still) missing something?



Title: Re: Shimming Woes
Post by: fiat-doctor on January 24, 2014, 01:35:10 PM
It's just me, but I think you've got it.  :)
Title: Re: Shimming Woes
Post by: Rikugun on January 24, 2014, 08:24:44 PM
Even if there's nothing to this, it's been a great brain exercise. I've been starved for bike stuff with a foot of snow and single digit temps. This taught things about the bike I should have known already.  >:(  It also refreshed my memory on things I once knew but have forgotten. 
Title: Re: Shimming Woes
Post by: dingleberry on January 25, 2014, 12:55:45 AM
I'm having trouble getting my head around this. Are the rear valves open and closed the same duration as the front?
Title: Re: Shimming Woes
Post by: fret not on January 25, 2014, 01:29:24 AM
Yes, same cams.
Title: Re: Shimming Woes
Post by: Rikugun on January 25, 2014, 09:45:58 AM
dingleberry - it's not the lift or duration that's in question but rather the rear cylinder valve timing. POD is suggesting that valve opening and closing events (expressed in crankshaft rotation degrees) of the rear cylinder is different than that of the front. There is a formula using those numbers that gives a "lobe center" value that is typically within a range. The closer the lobe center value is to either extreme of the range gives certain engine performance characteristics as outlined earlier in a table compiled by POD. Lobe center formula shown 2/3 down this page: http://www.muzzys.com/articles/lobe_centers.html (http://www.muzzys.com/articles/lobe_centers.html)

POD recognized Yamaha went to the trouble of marking the cam sprockets for front and rear, not just intake and exhaust. Why would this be if the cams are the same front and rear? He also noticed that when installed, the locking pin orientation  - which coincides with the lobe - was different between the front and rear cylinders relative to the valve cover gasket mating surface. He then hypothesized that the front and rear cylinders cam timing were not the same. Moreover, they could be easily changed by simply reversing the cam sprockets. Since there are separate intake and exhaust cams, the lobe center value could easily be altered. Contrast to a single cam with both intake and exhaust lobes which would have to be replaced (with different lobe-center grind) to accomplish the same thing.
Title: Re: Shimming Woes
Post by: dingleberry on January 26, 2014, 02:41:07 AM
Ok, getting it now. That link was quite helpful, thanks.
Title: Re: Shimming Woes
Post by: Rikugun on January 27, 2014, 12:20:22 PM
Quote from: ProphetOfDoom on January 23, 2014, 04:26:51 PM
No references I could find in the archive.  the cams are well documented in the service guides, except for timing, which is understandable as it's fixed by the pin.  Precise timing can be easily worked out with a degree wheel (I have instructions on how to make one on your printer somewhere.

POD, have you given the degree wheel idea any further thought? I guess the proper way to do it would be with the stator cover removed using the rotor bolt but what a PITA....  Had you thought of another method?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 27, 2014, 09:38:02 PM
Using the rotor bolt to mount the degree wheel is the usual way, with a piston stop down the spark plug hole to measure TDC, and a dial test indicator on the shim bucket to measure valve actuation.
 
If you were to trust the etched TDC markings (misplaced on the majority of bikes) then backlash is not such a big hairy deal, you could I suppose use a degreeing wheel on the cams or rear wheel (in gear) or even on the socket you turn the crank with.  Set to zero as you pick up the backlash and only turn one way.

Me, I'd just do it the "proper" way  Cam timing is too critical to risk getting it wrong.  It's not such a pain in the botty, but there's the issue of a $20 gasket and an oil change I suppose.

Title: Re: Shimming Woes
Post by: pinholenz on January 27, 2014, 10:32:40 PM
Hi there POD. Is that pesky 400 running now or did you end up buying a Corolla?
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 28, 2014, 12:09:16 AM
It's sprung an oil leak in the valve cover I'll take a look at tomorrow.
I couldn't bring myself to get a Corolla, so I got one of these
Title: Re: Shimming Woes
Post by: pinholenz on January 28, 2014, 12:16:17 AM
Love your work!!
Title: Re: Shimming Woes
Post by: dingleberry on January 28, 2014, 02:37:52 AM
Whoa, look at all the smoke coming out the back. Either that citreon is rooted or it's the getaway car from the Rainbow Warrior.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 28, 2014, 06:02:07 AM
Quote from: pinholenz on January 28, 2014, 12:16:17 AM
Love your work!!
Its a funny old world.  Some people get to make a great living driving stupidly fast cars, others hardly get by giving hand jobs to Ukrainian sailors.  Somehow it doesn't seem fair.

Quote from: dingleberry on January 28, 2014, 02:37:52 AM
Whoa, look at all the smoke coming out the back. Either that citreon is rooted or it's the getaway car from the Rainbow Warrior.
Mine smokes like that.  I thought it was normal for French cars.
Title: Re: Shimming Woes
Post by: Re-Vision on January 28, 2014, 07:13:26 AM
Renault's don't smoke, don't start either.      BDC
Title: Re: Shimming Woes
Post by: Rikugun on January 28, 2014, 10:10:00 AM
Quote from: ProphetOfDoom on January 27, 2014, 09:38:02 PM
If you were to trust the etched TDC markings (misplaced on the majority of bikes) then backlash is not such a big hairy deal, you could I suppose use a degreeing wheel on the cams or rear wheel (in gear) or even on the socket you turn the crank with.  Set to zero as you pick up the backlash and only turn one way.
I have considered the degree wheel on a deep socket but wondered about repeatability and indexing it each time it was removed. Do you happen to know how many teeth are on the cam sprockets?

Title: Re: Shimming Woes
Post by: Re-Vision on January 28, 2014, 10:52:00 AM
Quote from: Rikugun on January 28, 2014, 10:10:00 AM
Do you happen to know how many teeth are on the cam sprockets?

Mine has twenty-eight.    BDC
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 28, 2014, 03:20:29 PM
Quote from: Rikugun on January 28, 2014, 10:10:00 AM
I have considered the degree wheel on a deep socket but wondered about repeatability and indexing it each time it was removed. Do you happen to know how many teeth are on the cam sprockets?
I tried that, but there's a lot of slop in the bolt - socket.

28T on the XZ400 also, 42T down below.

Title: Re: Shimming Woes
Post by: Rikugun on January 28, 2014, 06:21:51 PM
OK, thanks to both of you.
Title: Re: Shimming Woes
Post by: dingleberry on January 28, 2014, 11:16:56 PM
Quote from: ProphetOfDoom on January 28, 2014, 03:20:29 PM

I tried that, but there's a lot of slop in the bolt - socket.



Man, I have a lot of trouble with that too!
Title: Re: Shimming Woes
Post by: dingleberry on January 28, 2014, 11:20:34 PM
Ukrainian sailors have 42 teeth? Crikey
Title: Re: Shimming Woes
Post by: Walt_M. on January 29, 2014, 04:33:51 PM
POD, are you saying the cam drive sprocket is not twice the tooth count of the driven sprocket? Or is there another gear in there I don't know about?
Title: Re: Shimming Woes
Post by: dingleberry on January 29, 2014, 06:34:18 PM
The bottom gear (42T) has an inner gear that's part of it (21T) that drives the cam chain to the cam sprockets (28T). The bottom gear (42T) is driven from the crank shaft gear (28T). I haven't done the math, but I guess the Yammy guys did to arrive at a 1:2 ratio.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on January 29, 2014, 09:56:34 PM
Quote from: dingleberry on January 29, 2014, 06:34:18 PM
I haven't done the math
(28 / 21) x (42 / 28) = 2
Title: Re: Shimming Woes
Post by: Rikugun on January 30, 2014, 10:21:39 AM
I'm aware of the other gears but only needed the top sprocket count to calculate lobe center shift per tooth.
Title: Re: Shimming Woes
Post by: injuhneer on July 07, 2019, 10:52:01 AM
Quote from: Prophet Of Doom on January 01, 2014, 07:00:31 PM
Has anyone noticed that the angle of the cams is different front & rear? (back onto the 550 now)

Obviously on the front they both point in at TDC, and rear they both point out - that's because they are the other way around.  But the actual angle is different (front lobes stick up more at TDC) so the rear will push the valves down earlier in the cycle than the front.

My assumption would be that this makes one cylinder stronger at a particular rev range, and so broadening the power band to make it more rider friendly?

Any thoughts on this? Could judicious cam re-timing get a free HP boost over a tighter rev range?

BTW I'm also inverting one cylinders cams 180 degrees (aka twingle, twumper, big-bang, close firing V)

The reason is far simpler. It is a V twin. That means all events are spaced by the angle of the V. Rear cylinder TDC and front cylinder TDC are separated by the V angle. Therefore all timing events are separated by that same angle in their respective cycles.

These pistons do not reach TDC simultaneously like a twingle or a flat plane crank engine.
Title: Re: Shimming Woes
Post by: The Prophet of Doom on July 09, 2019, 01:37:06 AM
Quote from: injuhneer on July 07, 2019, 10:52:01 AM

The reason is far simpler. It is a V twin. That means all events are spaced by the angle of the V. Rear cylinder TDC and front cylinder TDC are separated by the V angle. Therefore all timing events are separated by that same angle in their respective cycles.

These pistons do not reach TDC simultaneously like a twingle or a flat plane crank engine.
I'm not disputing this, but can't work it out in my head.  where is my thinking going wrong?


There are two TDC marks.  One for the front, one for the rear.  The picture shows the index marks straight upward, but in reality this never happens.  The front index is upwards when the flywheel is at the front TDC mark, the rear when it's at the rear TDC mark.  Each cam's indexing mark corresponds to TDC for that individual cylinder, so they are already 70 degrees out of phase. 


In the picture, the pins (which correspond to the lobes) are splayed differently so the degree before TDC for that cylinder must be different, and the rotation degrees between intake opening and exhaust opening also different.  N'est ce pas?


My engine is in tiny wee pieces, but I think I need to take some accurate measurements as I put it back together again.
Title: Re: Shimming Woes
Post by: injuhneer on July 10, 2019, 10:26:43 AM
It would help to have a chart of timing events. I haven't found one yet.

The rear head is reversed in relation to the front of the engine. That means the relative rotation of the cams is opposite. The timing of cam events is the same. If you look at the cams independently then the rearmost exhaust cam @290* is in the same position (pointing rearward) as the front-most exhaust cam was @290* before. The same is true of the intake cam. At 0* the front intake cam is pointing forward. At 290* the rear intake cam is pointing forward.

Does that help? Look at the cams individually rather than pairs (I & I, E & E) and you will see it. Same orientation only 290* (or 70* depending on your perspective) apart in cycle.