Yamaha TRX850 Enthusiasts Forum

Hi all,
Coming home the other day one cylinder seemed to lose power, and then a high pitched, and LOUD, rattle started coming from the right (i think?) cylinder; at idle or under no load it disappears, but past about 2000 revs it starts and gets louder and higher pitched as the revs rise.

Not sure what it is, thinking maybe a ring? The oil was pretty low too, i put about 2-2.5L in afterwards but this didn't help (a bit late i guess ).

Before i go pulling camchains etc. off i'd like to have a workshop manual, is there a downloadable one?

Thanks, Kirk.

Kirk - you have a pm

Thanks Jak!
I thought i'd seen it on here before but couldn't remember where!

I'll head to the shed now then.

You added 2-2.5 l of oil??

Oke then, lets pray.

you prolly gonna need it m8.

My bets are on the cam chain tensioner or guides. At least I'm hoping so...

The worst case could be 'another' camshaft journal seizure...

Well I got the manual sections i needed off the trxfiles site, and started stripping the top end. down to looking at the camshafts, camchain etc, can't see anything obviously broken yet.
Max, how would I check for chain tensioner or camshaft journal problems? would they be visible? 'Cos otherwise i'll just keep stripping until i see a busted ring or valve or something.
Thanks for the help all, and yes i suppose i should have picked up the oil level a bit earlier!!

I think you'll find them quite visible, but yes you need to start breaking it down in order. You can tell if it's the cam chain tensioner or guides when you pull off the valve cover and find the chain loose (and by looking down in the chain tunnel with a flashlight, torch or whatever you guys call them and see damaged guides). Camshaft journals (what the cam rides on in the head) will show scoring / gouging or other signs of lubrication failure and seizure.

Kirk wrote:Hi all,
Not sure what it is, thinking maybe a ring? The oil was pretty low too, i put about 2-2.5L in afterwards but this didn't help (a bit late i guess ).

If you have added that much oil to get the level back up you are looking at some serious damage due to oil starvation - sorry bit it ain't gonna be good news.

My money would be on big end having gone - possibly even bending teh crank?

OK, have stripped head and block off, the rings look alright, valves look alright (without pulling them out to check thoroughly), but there is one thing that looks sus.
No. 2 piston slides side to side on its mounting to the rod, so does no. 1. But no. 1 also rocks up and down by about 1-2mm at the other end (bottom) of the rod; ie. where the rod mounts onto the crank, no. 2 doesn't do this.
Would this indicate a big end bearing failure on no. 1 as phuk suggested?
If so, any ideas on how to check if its bearing or crank thats failed?

Thanks heaps guys, I'm pretty handy pulling apart basically any part of a car or bike but never been inside an engine before, so I'm a bit nervous!!
Thanks again, Kirk.

It sounds as if the bearings have gone - easiest way to check is to whip the rods off and have a look.

My guess is that they are now in a million tiny pieces in the oil. Crank is possibly OK (you may be lucky) but I would do a complete tear down just to be on the safe side. In fact I would do this anyway to clean the motor out.

I agree, and be prepared to be BATHED in oil. Oil that's probably left over from when they filled it at the factory. It's also a good time to clean the sludge out (you'll find plenty in the oil tank) and this may have been a factor in the first place, though it normally occurs in the top end.

Gee, you guys make this sound like its going to be sooooo much fun!

Sorry Kirk - after putting in 2litres + of oil you've been re-named "prostitute" - 'cos I ........ motors. Hope it doesn't cost you too much. TRX being wrecked at Western Bike Wreckers NSW. Might be worth a call if it all goes pear shape.

KIRK just following on from GLEN bits for bikes had a hotted up motor for 2 grand. Good luck.

Kirk, if there is too much damage, Tony (hairdo429) has a motor for sale for $500 might be worth a phonecall.
Terry