Motor noise, Help me !

My bike is making one noise too loud, chain like noise in motor!, but I was convenced that the problem was the timing chain , I replaced it but the noise don´t go!!!.

It is all time, but idling is more easy to hear it.... Please HELP ME!!.

WR400´99 Stock, 12000km (7200mile) so so. I don´t race it, I tour it too much.

chain tensioner OK?


'99 WZ/YR (you choose!) with ALL YZ mods, de-octopused, DSP Doug Henry airbox w/ velocity stack, FMF PowerBomb header, Stroker SX-1 silencer, SS front brake line, forked over by Pro-Action (and then fixed by me), OEM YZ tank, IMS YZ seat, gray wire severed, carb mods by Jim Dean, Andy in OZ, & Sir "Taffy" from Jolly Old England, AMA, NESC, and I use MOBIL 1 Oil, with ZERO problems.

Yes, it is OK. I remove it and test it, work very good!

do search on primary gear noise & counter balancer gear - should help you out.

did you recently adjust the valves? I installed the cams incorrectly in my bike - 1 tooth off - and it was the cause of the noise in my bike.


I don´t search here!. Where are they?. "Counter" balancer gear is behind of water pump or of the other side of the motor?.

"primary gear noise", I don´t think, the noise is all time, included when it isn´t on first gear. ("primary gear noise", do you refer to first gear?).

And the cam are ok, the noise is before the change of the timing chain.

Try these links:

You can search on my name and come up with additional info.

Primary drive gear & counter balancer gear are on the right side of the engine, between the clutch basket & water pump.

Hope this helps,


[This message has been edited by Brian Meadows (edited 06-26-2001).]

Ok, and THANK YOU. I´ll search here!.

I live in Argentina and my english is too bad... Do you understand me without problem?

All link are same!

What do I do?

Originally posted by Elian:

("primary gear noise", do you refer to first gear?).

I think they are talking about the primary drive gear on the crank that drives the clutch. But it is the gear behind this one that drives the counter balancer, it is secured to the crank with a straight key. On some ’00 YZ/WR bikes this gear wears a groove in the key due to the to and fro resistance of the counter balancer.

Just about everybody suspects some kind of valve train problem when they hear the noise this makes.

Here are some old posts on the YZ side about this problem:

Primary Gear Noise and Solution

Can’t find any reason for that noise

Hope this helps.

Thank...I will try it, but first I must to translate it. Later tell you.


Thanks, Hick. Not sure why I couldn't get post the correct links....


Thank Eric!

Hi, I can´t find the noise in my motor. This weekend I pulled off the rigth crankcase, the nut of the primary gear and the CB driven gear was very tight and there was not freeplay, anyway remove the nut and washer of the primary gear and this was OK, the CB wanderfull, the straight key like new. Then I´d remove the nut of the CB driven gear, ALL WAS OK!.

Later, a turn the crankshaft left and right, and I feel a tiny “hit” (tic-tic-tic). Then I decide to remove the cam and T-chain, turn again the crankshaft (left-right-l...-r...-l...-r...) and the hit still is there (then I said the problem is in: the piston pin – rod – bearing – pin crank). Remove the cylinder head, after it the cylinder and piston together (to avoid replace the rings). I FOUND A BIT OF FREEPLAY IN THE PISTON PIN WITH THE ROD, AND A “VERY TINY BIT” FREEPLAY IN SOME POSITIONS IN THE CRANK PIN (moving up-down).

1- Is the piston pin freeplay normaly? What is its limit?

2- Is the crank pin freeplay normaly? What is its limit?

Please helpe me, I´ll appreciate very, very much!. Thank you.

This tool that you mention, is like gauge (sonda en español)?

Ther manual said:

SMALL END FREE PLAY = 0.4 ~ 1 mm. (0.016~0.039in).

Is it the free play side to side between the pin and the piston?

Could it be the kickstarter mechanism which disengages the kickstart gear has failed? This happened to me after a mean kickback when I was starting the bike one day. The bolt holding the plate which disengages the kicstart gear when the lever is in the normal position broke off, and the bike made a terrible rattle noise. It is under the clutch. Check there.

Good luck


Pretend it's flat and give it the gas.

I don´t think that. but When I pulled off the crankcase cover and clutch basket, I found this gear with freeplay!. All on his place, but whith free play.

This free play is OK?.

Elian, do you have the owners manual. Allthe specs are there. i found it invaluble when rebuilding my top end over the winter. I have the same bike as you, '99 YZ400. Some side play is normal but up down should be minmal. Please get a telescopic I.D. mesuring tool that you can insert and then mesure with a micrometer ( for the small end on rod ). You can estimate play in rod only unless you remove it though. Side to side no problem. Good luck.

Does any body knows what is the limit freeplay, between pin and piston?

Mine was doing the same thing. Sounded like Loose timing chain but I replaced that woodruff key n noise went away. However, now when I have it in gear and gas it there is a delay in the rpm. Like it bogs down then revs up. Anyone know why?

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