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Shimming Woes

Started by The Prophet of Doom, November 15, 2013, 02:27:35 AM

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Fuzzlewump

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?
Know ye not that ye are a gremlin?? Thou hast no quarter here- flee now from me!!

fret not

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.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Rick G

Fuzz, there is a lot of machinery being turned when you rotate the crank. I see no advantage to turning it the wrong way.
Rick G
Go soothingly on the grease mud, as there in lurks the skid demon
'82.5 Yamaha XZ550 RJ  Vision,
'90 Suzuki VX800, 1990 Suzuki DR350.
'74  XL350   Honda , 77 XL350 Honda, 78 XL350 Honda, '82 XT 200 Yamaha, '67 Yamaha YG1TK, 80cc trail bike

The Prophet of Doom

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

Fuzzlewump

You're welcome, Prophet, and thank you everyone else for correction and guidance on my post.
Know ye not that ye are a gremlin?? Thou hast no quarter here- flee now from me!!

The Prophet of Doom

#45
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)

fret not

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.
Retired, on the downhill slide. . . . . . . . still feels like going uphill!

Rikugun

#47
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
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

The Prophet of Doom

#48
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?

Rikugun

Don't ask me, I've never even had the head off one of these things....   :P  :)
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

Rikugun

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?
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

The Prophet of Doom

#51
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.

Rikugun

#52
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.
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

The Prophet of Doom

#53
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.

dingleberry

#54
"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.
You like, oui?

Rikugun

#55
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?
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

fiat-doctor

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

Rikugun

#57
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?



It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan

fiat-doctor

It's just me, but I think you've got it.  :)

Rikugun

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. 
It is far better to grasp the universe as it really is then to persist in delusion, however satisfying or reassuring.  Carl Sagan