Yamaha TRX850 Enthusiasts Forum

Didn't get to ride my TRX much after buying it last year. One thing i did notice with it is a light engine rattle, sounds like cam chain to me. It is OK from cold but gets worse as the engine warms up. I have changed the oil etc and the tensioner was replaced 10,000 miles ago. The engine only has 24,000 miles on it, would you expect a chain to be noisy at that mileage? Also could the carbs being out of balance cause the chain to rattle?

It's very difficult to diagnose noises on a forum but I would say that some TRXs are very noisy. Have you had a chance to listen to any other to see what is nromal. My one clatters like feck and I know all is good with it.

I'm kinda curious as to why any cam chain work would be required on a 14k engine. It's also a bit weird that the noise gets worse as the engine warms - that doesn't generally happen with cam chain rattles. At 24k I'd be guessing at valves.

To help narrow it down, does the noise change as the revs rise? Does the noise go away if the bike is idling in neutral? Or only when under load?

Unusual for the noise to beome greater as it warms up , the reverse is normally true

I find that if the motor starts 1st touch of the button then the valve clearances will be ok .... a little longer to start as they need adjustment

Any noticeable ratling on a warm engine is going to need investigation Id say

I had one of my engines that developed a light rattle when warm, it got worse and developed into a knock and big end failure. A cam chain will rattle from cold. I would say that it is a component relying on oil pressure! as the engine warms the oil gets thinner and the oil pressure drops. Could be the early stages of crankshaft failure? Immediate investigation required.

Thanks for the replies.
Not had the chance to listen to another TRX never seen another one around these parts or a TDM. The bike starts on the button, but i will check the clearances but is not only tight clearances that would cause starting problems?
I am sure the noise is top end and not the crank. The noise is very light at idle and increases when taking the revs up, after about 3000rpm the noise tails off. That or other engine noise drowns it out. Revved hard under load the engine is quiet enough another reason i don't suspect the crank.
I can only suspect the chain tensioner was replaced to try and cure the problem by a previous owner. My experiance is with two stroke bikes, but the few fours i have owned have not been as noisy, one of them was a thunderace. First four stroke twin though.
Think i may have to have a peek under the cam cover.

cycloneranger wrote:Thanks for the replies.
Not had the chance to listen to another TRX never seen another one around these parts or a TDM. The bike starts on the button, but i will check the clearances but is not only tight clearances that would cause starting problems?
I am sure the noise is top end and not the crank. The noise is very light at idle and increases when taking the revs up, after about 3000rpm the noise tails off. That or other engine noise drowns it out. Revved hard under load the engine is quiet enough another reason i don't suspect the crank.
I can only suspect the chain tensioner was replaced to try and cure the problem by a previous owner. My experiance is with two stroke bikes, but the few fours i have owned have not been as noisy, one of them was a thunderace. First four stroke twin though.
Think i may have to have a peek under the cam cover.

Reading about a lot of different bikes with the same symptom, a carb balance made a huge difference...
Also, if little/big end you can pop off a cap while running...if sound disappeares then that side has issues....