Clanging noise, YZ426


12 replies to this topic
  • Magnus_N

Posted November 17, 2004 - 11:42 AM

#1

Hi

My friend have a YZ426 (-01?)with some clanging noise from the engine and we thought that the noise came from the valves.
When i checked the clearance between the camshaft and the valves i got some strange measures.
All measuring was done with a cold engine.
The first thing i did was to align the "top dead center" mark on the rotor with the mark on the crankcase cover.
The piston was at the top of it´s stroke and the two punchmarks on the camshaft gears was aligned with the top surface on the cylinder head.
In this position i measured all 5 valves and the right and left intake valves was within specifications according to the manual but i could not even get the smallest feeler gauge between the center intake valve and the camshaft.
Both exhaust valves measured below the specified limits in the manual and if i remember correctly the clearance was approximately 0.17mm (0,20-0,25 is manual spec) on both valves.
So my question is should the center intake valve have such small clearance between the camshaft or should it be the same as the other two intake valves?
The exhaust valves was slightly below the specified limit could this occur due to severve wear between the valve seat and the cylinder head?
When i removed the crankcase cover i noticed that the balancer shaft probably have worn bearings because when i pushed it upwards it did make a metallic sound and the play in the bearing can be felt when pushing the shaft in various directions.
Is it possible that the worn bearings on the balancer shaft makes this sound and is this a common problem?
We have now removed the cylinder head,cylinder and the piston from the engine and i visually examined the parts but could not find any unusual wear the next step is to disassemble the cylinder head and take a closer look on the valves.
I could not specify the noise from the engine better because i have not heard it myself, but my friends described it to me.
The noise appears even when the engine is on idle so it probably wont come from the transmission.


Best regards

Magnus :cry:

  • TxRenegade

Posted November 17, 2004 - 02:52 PM

#2

I had a problem with my old DRZ, it was the valve retainers were wearing out and allowing the valve stem to sit lower. You might see if the cam is actually hitting the valve button or the retainer.

Good luck...............

  • Magnus_N

Posted November 17, 2004 - 03:20 PM

#3

I had a problem with my old DRZ, it was the valve retainers were wearing out and allowing the valve stem to sit lower. You might see if the cam is actually hitting the valve button or the retainer.

Good luck...............


Thanks TxRenegade for the answer, :cry:

But if the valve retainers was worn and allows the valve stem to sit lower would not the clearence between the camshaft and the valve be bigger then?
It confuses me that the clearance is smaller than manual spec on the center intake valve, The only way the valve stem could sit higher must be if there is severve wear on the valve seat.
The exhaust valves also had slighty smaller clearance than the specified limits in the manual how could this happen???
We should have done a compression test on the engine before we disassembled it but now it´s too late.
A low compression would have indicated that either the piston rings or the valves was defect and that would have make everything easier....


/Magnus

  • grayracer513

Posted November 17, 2004 - 06:03 PM

#4

I had a problem with my old DRZ, it was the valve retainers were wearing out and allowing the valve stem to sit lower. You might see if the cam is actually hitting the valve button or the retainer.

Good luck...............


It sounds like the two heads are not laid out the same way. A YZ cam can't contact the adjusting pad, because it's under the cam follower. The keepers could work their way up the valve until they hit the adjusting pad, but after that, there would be nothing to push the valve further down between the keepers.

I have encountered valves at less than zero clearance before, and I have a couple of theories about how that might happen. The important thing is to set it back to the right clearance. You will have to do a trial fit of a shim about 3-4 sizes smaller to get a baseline reading for the correct shim.

As far as your rattle, also confirm that the counter balancer drive gear is tight (on the clutch side). You seemed unsure if it is a '01. If it is an '00, it has a key on the balancer shaft that has a reputation for exactly this sort of thing. If it's a '01 or later, it will be splined, but could still be loose.

  • TxRenegade

Posted November 18, 2004 - 12:36 PM

#5

No the clerence would be less due to the valve setting lower, and the bucket hitting the retainer instead of the shim.
Grayracer, I believe the heads and drive trains are the same, I may not have explained it very well. Mine has a "bucket and shim" set-up under the cam, and I believe the 426 does also. I kinda hope so, I am going to buy one tomorrow, it's an 01 426f.
Hopefully that help clear things up.

  • grayracer513

Posted November 18, 2004 - 01:12 PM

#6

Yes, tha does describe the YZ set up. I got thrown off when you said the cam might hit either the pad or the retainer. I started thinking of an older pad on top of the bucket set up like the first Kawasaki fours had. :cry: :cry:

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  • Magnus_N

Posted November 18, 2004 - 02:41 PM

#7

I have never disassembled a cyl head like this but when i studied the part list i think i figured everyhing out.
There are two halves of a locking device that connects into the grooves on the top on the valve stem and if there are wear between these two and the upper valve retainer then the retainer would be pushed further up against the valve lifter than normal.
And if the retainer is in contact with the valve lifter then the valve lifter is higher than normal and that would explain the small clearnace between the camshaft and the valve lifter.
When the camshaft press against the valve lifter then the lifter must be pushed through the "air" and compress the spring a little bit before its makes contact with the adjusting pad.
If it´s work like this then it would explain the clanging sound.
If this does not make any sense to you please feel free to correct me.


/Magnus

  • TxRenegade

Posted November 18, 2004 - 02:59 PM

#8

Yes that is basically how it works. The retainer wears out and lets the retainer rise up and hit the bucket. This is something that is rare, but it does happen. Have you noticed you fuel usage getting worse sense the noise started. Mine was, it was caused by the valve not closing all the way. I refreshed the top end, and it gained a lot of power as well.

Later.................

  • grayracer513

Posted November 18, 2004 - 03:05 PM

#9

I still suggest checking your balancer shaft for your clanging noise, as I said earlier.

The cam follower has a bit of a raised button on its underside where it contacts the adjusting pad so that even if the pad were well below flush, there is almost no chance the follower will contact the spring retainer, so that's not it.

Other places the noise could come from are broken or missing chain guides. There's one in the top of the cam cover, one on the tensioner, and a long one on the front side of the chain. This one can break and drop down to where the counter balance weight hits it.

If you pull the cams, there are 2 easy places to screw up. One is by dropping the half ring bearing locators under the camshaft ball bearings down into someplace where they are hard to get out. The other is by improperly torquing down the cam caps when you go back together. Do it in steps, with a real torque wrench, and don't exceed the spec for any reason. I actually use 75 inch/pounds instead of the 86 it calls for.

  • Magnus_N

Posted November 18, 2004 - 03:13 PM

#10

Yes that is basically how it works. The retainer wears out and lets the retainer rise up and hit the bucket. This is something that is rare, but it does happen. Have you noticed you fuel usage getting worse sense the noise started. Mine was, it was caused by the valve not closing all the way. I refreshed the top end, and it gained a lot of power as well.

Later.................



Ok, It seems that replacing the retainer and adjusting the valve clearance would solve the problem.
I cant answer the question regarding the fuel usage now must ask my friend first.
Thanks for all the replies!!

/Magnus

  • Magnus_N

Posted November 19, 2004 - 02:21 AM

#11

I still suggest checking your balancer shaft for your clanging noise, as I said earlier.

The cam follower has a bit of a raised button on its underside where it contacts the adjusting pad so that even if the pad were well below flush, there is almost no chance the follower will contact the spring retainer, so that's not it.

Other places the noise could come from are broken or missing chain guides. There's one in the top of the cam cover, one on the tensioner, and a long one on the front side of the chain. This one can break and drop down to where the counter balance weight hits it.

If you pull the cams, there are 2 easy places to screw up. One is by dropping the half ring bearing locators under the camshaft ball bearings down into someplace where they are hard to get out. The other is by improperly torquing down the cam caps when you go back together. Do it in steps, with a real torque wrench, and don't exceed the spec for any reason. I actually use 75 inch/pounds instead of the 86 it calls for.


I was writing my previous message when you posted this....
I have checked the chain guides and they seems to be ok.
I know how important it is to use a quality torque wrench when assembling engines and if the bolts on the cam caps are overtighten then the camshaft probably would be stuck and cant be rotated.
It seems that replacing the balancer shaft bearings and disassemble the cyl head so every part can be visually examined and measured would be the best thing to do.


/Magnus

  • flyinguitars

Posted November 19, 2004 - 06:01 AM

#12

Hey,
I just adjusted my valves last week....mainly because I also had a "clanging" noise. I put a post here at the time. Anyway, I found my exhaust valves to be loose. I chalked it up to possibly the wrong measured clearance when I installed the 450 exhaust cam...but it just doesnt add up. Now after reading this post, Im wondering if my exhaust valve cotters are worn?? Im assuming thats what you guys are calling the retainers?....I had to go from a 180 to a 195 shim. It has quieted the noise down, but im wondering now if worn cotters have anything to do with it?

  • grayracer513

Posted November 19, 2004 - 04:17 PM

#13

Hey,
I just adjusted my valves last week....mainly because I also had a "clanging" noise. I put a post here at the time. Anyway, I found my exhaust valves to be loose. I chalked it up to possibly the wrong measured clearance when I installed the 450 exhaust cam...but it just doesnt add up. Now after reading this post, Im wondering if my exhaust valve cotters are worn?? Im assuming thats what you guys are calling the retainers?....I had to go from a 180 to a 195 shim. It has quieted the noise down, but im wondering now if worn cotters have anything to do with it?


FG,

The "cotters", one of their many proper names, and the one Yamaha uses, I call Keepers, another name they go by. The retainer I mentioned is the valve spring retainer. The YZ manual just calls it a valve retainer. Picture how the assembly looks with everything in place. The cotters fit into grooves in the valve stem. The spring retainer is pushed up against them by the valve spring. The valve stem sticks up above the cotters by a good 1/16" or so as I recall. The retainer has a precisely bored recess on the the top to allow the adjusting pad to drop into place. If you could see through this assembly from the side, you would see the pad sitting squarely on top of the valve stem, and there would be that 1/16" or so of space between the cotters and the pad.

Anyway, the scenario offered by TxRenegade is this: the built in forces here would like to push the spring retainer off of the top of the valve stem, but the cotters hold it back. After a while, having the valve opened and closed 80+ times a second begins to beat the cotters and the groove in the valve stem up, and the cotters begin working their way up the stem. If a lot more of this were to take place than I think is possible, or there is considerably less than 1/16" of space there in the first place, the cotters might slide up the stem to the point where they were in contact with the pad also.

Once it gets to this point it will, if it continues, run completely out of clearance, but then it should pretty much stop, because then, the cam and follower would be holding the spring retainer on. The valve could possibly chuckle back and forth between the worn keepers and the adjusting pad, but it seems like a stretch. No pun intended.

The point is that worn cotters would only be capable of reducing valve clearance, whereas yours increased. Why would it increase? Something would have to wear, or valve become bent or trap a chunk of carbon on a valve seat, or as you said, you may simply have done it wrong the first time through.

That help?





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