Yamaha TRX850 Enthusiasts Forum

Good Afternoon TRX enthusiast,

My bike is second hand and has 58000 km on the ODO.

The engine is making a bad noise, especially in hot condition (cold condition : no noise), and especially at accel-off.
It is similar to the one on this Youtube video at 0.48 sec : http://www.youtube.com/watch?v=_NQkFpuFr4c. (it is not the clutch bell noise that you here at Idle)

I already checked (and change if applicable) the valve clearance, chain tensionner and Timing Chain.

Still this annoying noise is here. So I opened the Cylinder.
Ovalisation (0,04 mm) and piston to bore clerance (0,065 mm) are within spec.

However, there is a big play between the pin and the small end (already 0,05 mm between the pin unwear surface (external) and the smal end...), which is to my mind not normal, and I think is the root cause of that noise.
1/ in hot condition, clearance are higher due to Thermal dilatation
2/ oil is less viscious.
3/ There are scratch mark on the small end inner.
4/ Play can be felt by rocking back and forth the pin in the conrod small end.

The pin is chrome plated so I have the feeling it is the connecting rod that has taken the wear...

My question is : 1/ Does anybody already had the same problem ? What do you think about my analysis ?
2/ I have not found in Haynes manual the dimensions for small end diamater, does anyone knows it ?
3/ Do you know a cheap way to get new conrods ? or repair the current one ?

Thank you very much for your support,
gdlbb.

Hello and welcome gdlbb.

Click on BOARD INDEX then go to DOWNLOADS, you will see a link for the TRX service manual. Click on the link and you will find what you are looking for there.
From memory the specifications are about 15 pages in.

Hi gdlbb, did you solve your problem? I have just rebuilt my top end and am now getting the same noise as in that youtoob link you posted. No idea what it might be.

Also it's getting very hot very quickly now. Something's not right!

Sounds like a loose timing chain from the video. I had similar sound at 47000 km and was easily fixed by tightening the adjuster. It is on the last click at the moment though. I ll need a new tensioner sometime in the 70 k mark I feel.

Not a noise I've experienced. Does sound timing chain-ish, though the ones I've heard (not trx) tend to be a "clickety" sound rather that a rapid click-click-click. Have you tried the old screw-driver-stethoscope trick to help pin-point the vicinity of where the noise is coming from?

Regarding your con-rod question; I have a motor pulled down for rebuild. While I never heard it running, the word was that it was reasonable with high km. Checking the sump there was some silver which I expected were from bearings, but it turned out to be the rod small-ends.

A few of us have bought rod's from partshark.com which was much cheaper than Yamaha. Cobba' may have had a set available if I remember correctly(?)

Okay, new timing chain ordered - should arrive today. But lead time on new tensioner is a few weeks away.

Having said that, the tensioner is not at full extension when I remove it. Not sure if something is stopping it getting to full extension...

Haven't tried the screwdriver stethoscope. Love the idea! I'll try it tomorrow.

New timing chain in. Noise significantly reduced but still present. And only after warm (ie, no noise when cold, or idling.)

Plan to just ride it normally and see if it gets better or worse.

iain wrote:New timing chain in. Noise significantly reduced but still present. And only after warm (ie, no noise when cold, or idling.)

Plan to just ride it normally and see if it gets better or worse.

Can u manage to it slightly tighter for a day or two to see if it reduces?

I've tightened it one notch on the chain tensioner ratchet but no change to the noise.

Took it to the bike doctor to have the carbies balanced. Apparently they were way out. Now she sounds better than ever! And overheating issue solved. Must have been running too lean.

As for the ticking noise, it's unanimous that it is the timing chain. And it is also unanimous that it is nothing to worry about. Which is a relief cos I am about to ride from Perth to Sydney (~4500km) and didn't want to do it on foot.

iain wrote:Took it to the bike doctor to have the carbies balanced. Apparently they were way out. Now she sounds better than ever! And overheating issue solved. Must have been running too lean.

As for the ticking noise, it's unanimous that it is the timing chain. And it is also unanimous that it is nothing to worry about. Which is a relief cos I am about to ride from Perth to Sydney (~4500km) and didn't want to do it on foot.

PERTH to SYDNEY....jeeeez....and 4500 Kay's......
Why would you want to go to SYDNEY.?

alextrx850 wrote:PERTH to SYDNEY....jeeeez....and 4500 Kay's......
Why would you want to go to SYDNEY.?

Haha. Should be a cool trip. Heading up through Vic high country. Might post some pics when I arrive.