Engine gurus please read:

[inanecathode]

I apologize for the length, but you guys are kinda my last hope. I'm hitting brick walls all over.

So i've been in a bit of denial lately about the status of my rd400. It runs and rides fine, but from the very day i put the new pistons and cylinders in it its clattery like crazy, just how it used to be, only this time it sounds like the left side. I thought it was normal at first, and it'd go away with the break in, but after putting about a hundred miles on it its got nothing but worse.

I'm super super mega bummed. It took like a month to get this whole thing dealt with, including several days worth of bugging the shop to get the parts done; i wasnt nagging them they said they'd have X done by tomorrow, i'd call them three days later and the part is still untouched, sure we'll do it tomorrow, another three days and yup, parts still not touched but it will for sure be done by monday. I gave them the cylinders and asked them to measure them and look at them for me because im not sure what i'm looking at. They said, yup needs an oversize, and they told me to get 20 thousandths over pistons, so i did. I then gave them the pistons with rings and all that happy shit and asked them to do their magic with them. After they got it done i asked if thats all i need to do, what the break in should be, and so forth. Everything seemed hunkey-dorey.

Anyhow, i was assuming this would fix the piston slapping it was having as the right bore was obviously partially seized at one point and it hogged it out a bit so the piston was loose. So with the brand new pistons and brand newly machined cylinders i put it together without a single problem, the rings were aligned right, wrist pin clips went in fine, nothing got into the case, the small end bearings were perfect, and there was no play at either the small end or the big end of the connecting rods.

I go to start it up and its clicky ticky, bordering on rattling when its coming down off revs. You accelerate and its quiet, but when you're on engine braking its clattering really loud.

I dont think this is normal, and i dont think its anything i did to it, all it did was put it together. The oil injection system is working fine, theres a tiny smidge of oil i added to the gas (barely 75 to one or so, very light mix to assist with the oil injection pump). The only thing i can think of is the shop somehow borked the boring, boring it too big or something.

Is there an irrefutable, concrete way to find out what exactly happened? I want to know that i didnt mess anything up because its certainly possible given the amount of delicate clearances and such. On top of that, if things get hairy with the shop i want some kind of way to prove that they're the ones that messed up, not me.

Considering i just got the parts done professionally at a shop, do you think i have any recourse to make them take it back and do it right and possibly buy me another oversize piston set? It miffs me so, but i dont like confrontation, and they would kinda have me by the balls as far as having a running bike or not, i dont have a job and im really kinda out of money as far as project bikes are concerned. I already put 300 dollars into the top end on this bike and i really cant afford to put another 300 for no reason at all.

[inanecathode]

Rods feel fine, nice and tight. Heres some pictures:

Piston top, looks normal from the charge blowing some of the carbon away



Intake port side, does that look funny to anyone? how its not evenly wearing?



Exhaust port side:



More cylinder goodness



This looks heavier than it is, theres no metal transfer and none of these marks are palpable



Other side




I brought the cylinder by the shop today to have them look at it. Noone knew what was what until the owner came up and had a look. He said it looks like heat or detonation. I didnt do anything to the mixture, and the injection system is working fine. I also know the difference sound wise between detonation and piston slap, that and its not happening how detonation does, instead of high load low rpm its engine braking, mostly high rpm (tho all over).

He then also said to check if my rings are upside down or something. They're plain rings, rectangular in every way, theres no up or down nor does the literature mention a proper orientation besides the rings being pinned in place.
He told me to check the timing (re: detonation) check the cylinder base gasket thickness (re: port timing) and check the rings to make sure they're in right.

You know i dont know much about interior engine stuff to be quite honest, and i do know a little tiny bit, it just doesnt seem that its detonating, the plug looks great and theres no damage to the top of the piston. Im not happy with the explanation i was given...

I think they're feeding me jive, and the cylinder wasnt bored right, what do you think?

[Kevin]

On the old suzuki's the rings did have a top and bottom side, don't know about the rd's. I would slide a feeler gauge between the piston and cylinder and look for 1&1/2 to 2 thousands clearance. You might sign up on the rd website.  http://www.yamaha-rd.com/forum/

[Rick G]

I typed a complete commentary and when i tried to send it my ISP  had dropped out . Its late I( 'll try again tomorrow.

[inanecathode]

I typed a complete commentary and when i tried to send it my ISP  had dropped out . Its late I( 'll try again tomorrow.

Duuuuuuude, you're the guy i was hoping would comment  :'(

[YellowJacket!]

Bent/warped crank?

David

[xswheels]

My initial reaction is where are the cross hatch hone marks? It is hard to judge, but it also looks like the ports were not chamfered. Picture #2 shows an old gouge at the 2 o'clock position that still remains after the rebore. It looks like an incomplete bore job, as if your cylinder is still out of round. Your replacement pistons are round and maybe they found high spots in the cylinder.
One other thing, you said there was no free play at the big end bearing. You should have some side to side free play when you move the connecting rod.

[xswheels]

One other thing that is not likely related to your problem, but could be addressed since you have the heads off is fixing your stud bore on the head in pic. #1. Three stud holes look normal, but one is tight against the cylinder stud as evidenced by the thread impregnation within the bore. What can happen is aluminum can be pulled up from the bore (when torquing your head nuts) and make your gasket surface uneven. Measure your head for straightness checking closely at the affected stud bore for a high spot. I would pass a tight drill bit through the bore and even consider running a slight countersink if there is indeed a high spot.

[Rick G]

OK here goes,  First the Yamaha rings are of the keystone pattern , that is ,they are flat on the bottom and have a slight slope on the top surface . The idea is to have the rings not stick in the grove when there is a carbon buildup , also  when combustion pressure builds up on the top of the ring , it causes the ring to press against the bore more tightly, and conversely to lessen pressure on the up stroke.
As to the bore, its a little rough to tell from a picture ,but it looks like a very rough ,slip shod job.
The cross hatch is at the wrong angle (should  be at 45 degrees to each other)  and is very ,very course .It looks like very rough stones were used in the finishing of the bore job.
The way its supposed to be done its bored on a boring bar , like a Quickway, and finished on a Sunnen hone, to the correct size . this looks like it was done with rocks. The accelerated wear on the pistons shows this.
They didn't bother to chamfer the ports at all. 

I would take it to another motorcycle shop or as a last resort, an automotive machine shop and have them check it for out of round,taper and piston clearance. Also get an opinion of the quality of the work.
If you want to talk about this , phone me . If you don't have my number anymore , H2 does , or PM me and I'll send it. I  talk fast and  type slowly , so I may have missed something and may have questions for you.

[motoracer8]

All of what Rick G. said is right on. Did you use OE Yamaha pistons? They look like Wiseco pistons to me, Wiseco pistons are forged, not cast and do require alittle more clearence, so they can be alittle noisey.
Back in the day we used to call them seizeco pistons, as most shops would set them up alittle too tight, trying to make a street bike quiet. On a race bike alittle piston clatter did not matter.

  Ken G.

[Ron_McCoy]

Ben,
Everything Rick and Motoracer8 have said is correct. It goes beyond that though. That cylinder has not been bored. It has had a hone run through it and you can see the honing pattern running through the siezure marks.  Also the bore is not round or straight as evidenced by the areas with no honing marks. Also you have aluminum smeared across the rings near the pin for the lower ring so this piston is toast.
Unless you are on the last overbore, you need to take your cylinders and the correct pistons to a reputable shop and have them bored.  The correct clearence is .0025. The ports hav to be chamferred to guide the rings back into the bore because they bulge out into the ports as they go by them.  Your lucky you haven't caught one on a port edge.  That destroys the piston, rings and usually the cylinder too.  I have built and raced RDs and if assembled correctly,  they are very reliable.  You might also check your squish band clearence.  Those bright marks on the piston can be caused by the piston hitting the head.
This is also more likely off the throttle too.  Once you get the mechanical issues worked out, put a set of 12 volt car coils on it.  You'll be amazed at the difference, better starting, better idle, and the plugs last far longer.

Good luck

Ron

[Rick G]

Ron , that was my suspicion that they were not bored , just a hone run through them, (a pretty course one at that) Its a little hard for me to tell from the pics. The voids in the hone pattern are a sure indicator.
These guys are crooks or don't know what in h**l there doing! Maybe both.

I've bored cylinders with just a SUNNEN hone , when a boring bar wasn't available, but you have to be careful and you HAVE TO KNOW WHAT YOUR DOING!

[inanecathode]

So i've got a couple opinions running on this one so far.

1) They were bored, but bored to big, as the clearance comes out to just about .004 possibly bigger. The loose piston is what caused the marks et al

2) They werent bored, as evidence by the hone marks running through the dark scratches.



For the second theory, the pistons are actually oversized though, is it possible to just hone the jesus out of it till its to size? Also, could the piston make the marks after the cylinder has been honed?



Im just trying to get my ducks in a row when i bring the parts back to the shop that screwed it up. Any advice?

Heres my post from the other day:

I took the cylinder to a proper engine machinist today. He measured it up and down top and bottom east and west and says that the machine job is fine, and it measures to 2.540" and at the greatest its out by about a thousandth way down the skirt of the sleeve probably due to the sleeve getting hot and expanding into the machine tool.

He also says that its flat top to bottom, and that its consistent all the way around. In other words, the bore is straight and true in every way. The only abnormality he spotted is how shallow the crosshatch angle is.

I measured the maximum piston size today (at the bottom of the skirt where the book says to measure) and came up with 2.536". The minimum (probably a bit smaller than this as it was measured at the top where it wears faster) cylinder diameter is 2.540". The difference being .0085" (of course this is cumulative so the clearance is actually half this). The book lists a minimum clearance of .0016" and .0018". That being a minimum i think i should be ok as far as clearance goes. I'm not an expert, but i dont think .002" shouldnt make this noise, right?

[Walt_M.]

I can't see how it could have been bored and leave all that carbon. When I had cylinders bored, they looked all shiny and new with very fine hone marks. Can you check the piston clearance?
Any chance some friends of Coil did the work for you?

[inanecathode]

Lol walt, no it was local.

This is after about a hundred or two miles. When i got the cylinders back they looked all shiny and new.

Heres my measurements (These are both measured at the right points, if anything the cylinder is a bit bigger):

Cylinder: 2.540"
Piston: 2.536"

The aluminum smear i think ron is referring to is flash glare, theres no metal transfer anywhere on any surface, pistons, cylinders, anything. Its all just visual marking nothing i can actually feel. I really hope this helps.

[Walt_M.]

There is still too much carbon in the bores. It looks like the rings aren't sealing. As for clearance, use a feeler gauge between the piston and the cylinder in the middle of the bore. Oh, if your oil injection is working, do not add oil to the gas. It doesn't need it.

[inanecathode]

Ok i'll do that. I'll be more comfy doing that ontop of just measuring it.
I cant measure worth crap :D

Man i just want to ride it so bad, if they wont end up fixing it i'll just put it together and ride till it blows up. Either way i need a new set of pistons and machine work so, bleh.

[Rick G]

Inane , I wish you lived closer , I'd love the run my glaze breaker through the bores , then your rings would seat.

You mentioned that the wrist pin needle bearing were ok , but you need to know what to look for,
the cage's should have none of the bluing worn off . If there is any gray showing on the outside , at the edges of the cage , you need new bearings.

[inanecathode]

Ok, so a minor update.
I took out the piston (one of the jesus clips shot off into the ether it seems so, at least im not tempted to reuse the clips) and took some better pictures. I also read some wiseco writings and other articles and they all suggest to use clearances suggested by the manufacturer, theres supposed to be a sticker with the clearance listed on it on the piston box:
(in case you're curious, the rd350 is the same bore, just a taller stroke, so the pistons are the same)




Theres some kind of galling right below where the piston rings sit. Theres some tiny missing pieces of metal missing, and its like the edge is trying to peel off. This might be what the marks on the cylinder are from.






The marks i errantly thought were just visual marks are in fact starting to become real marks. Theres definitely a 'feel' and 'sound' to these marks at least down where the skirt is:






So, i've got the piston, rings, and cylinder sitting in front of me right now, i'll go ahead and attempt to measure clearance and report back with numbers.
Something else i noticed, probably nothing, but notable. When i fit the piston in the cylinder and move it up and down, it feels like it gets really tight when the piston top nears the top of the cylinder, but loosens at the bottom, is this normal?


Another update:

Ok so, putting the piston skirt right in the middle of the cylinder bore, and pressing the middle of the feeler blade to curve it so the edges arent dragging, just the thickness of the blade, i can handily fit a .007 blade between the skirt and the cylinder wall.

Due to the lack of substantial physical metal loss on the cylinder and the piston i judge this to be a product of the final-machined finish size not cylinder wear. I'll hereby refer to this as "a jacked up machining job" and i'll be giving the machinist a visit tomorrow to see what he'll do about correcting this

Also, those verticle marks do coincide with where the head bolts are, i'll also be assuming this is due to the lack of a decking plate whilst machining.

Lets do this in a list:
1) Cylinder is bored too large
2) Cylinder was bored without a decking plate
3) Hone angle is wrong (way too flat)
4) Ports are not champhered (i just almost cut my finger on part of the exhaust port)

I'm going to try to be really nice and diplomatic about it, i get a funny feeling he'll just tell me to take a hike... I have no real way to prove that they have done anything wrong really when i think about it, they can just chalk it all up to user error.
I'm already super bummed, i was pretty excited to have such a cool, old, fast bike and it just evaporates just like every other potentially cool thing in my life  :-[

[Coil Coyle]

\ That cylinder has not been bored. It has had a hone run through it and you can see the honing pattern running through the siezure marks.  Also the bore is not round or straight as evidenced by the areas with no honing marks. Also you have aluminum smeared across the rings near the pin for the lower ring so this piston is toast.
Unless you are on the last overbore, you need to take your cylinders and the correct pistons to a reputable shop and have them bored. 

Good luck

Ron

Cathode,
            The cylinder wasn't bored, it might have been the second overbore already.
Really,
;)
Coil