Yamaha TRX850 Enthusiasts Forum

Hey all, pulled the tensioner out the other day (following all the rules i know to be good) and i think i still managed to skip a tooth on the inlet cam (I heard a tooth skipping kinda noise). But I'm having trouble finding what the cam timing should be at TDC on #1... The manual says that the cams should be 180deg away from one another on TDC of Compression stroke... I assume this means #1 Cyl.

But further down it says when installing the cams to "align the matching marks"

Now... so far, Ive got a point were the cams are 180 deg opposed as in the first case (but i can't remember if the timing mark on the crank is lined up at #1) but at this point the marks on the cam gears are not lined up... Exhaust is approximately level with the head (less then 1/2 a tooth out) and inlet is approximately 3 teeth counter clockwise. I was speaking with a guy at work who is a former Bike mechanic and TRX owner, and he said that without question the marks on the cam gears are suppose to line up, and the cams lobes should be opposed with about 150deg, not 180... Problem is that the manual doesn't mention the position of the crank when you line up the cams, last time you touch the crank in the manual is when your checking for clearance on #2 on TDC so one would assume they still have the crank in this position, However it would seem to me that you would set up the cams when #1 is top dead centre.

What's confusing me most is that it appears that i can set the cams to be 180deg opposed, OR i can set up the cams so the timing marks are lined up, and the cams appear to be 150deg opposed... but not both...

Anyone able to clear up the confusion?

Without turning the motor over then the chain should not be able to jump a tooth very easily just by removing the tensioner. Did you try putting the tensioner in adn winding the motor over a full cycle, or is it still sitting there as when disaster struck?

Sorry for the alignment, but i think it's visible anyway.

You should remove the two covers on the LH side of the engine. In the smaller hole You should line up the 'T'-mark as in the picture. If all is well and good, the marks on the camsprockets should line up with the head as in the pic below. Just to check that the cams are correct, also look for the small marks from above, as in the final picture. This last step is to ensure that You haven't put the cams 180 degrees wrog, as the sprockets have double markings.

I have probably nothing significant to add to the last very helpful post .... but ... is it a new camchain?

"Having trouble sorting your cam timing? Looks like the marks are out? - usually slightly retarded? This is because th TDM/TRX camchain seems prone to stretching (forget what Haynes book says ), not only do you run the real risk of geting timing a tooth out, it will rob considerable performance from engine. You can change camchain without taking engine out - through the oil pump cover, just make sure you use an impact driver to remove the 4 phillips screws. (killerwhale!)
Got 2 knackered (streched - about 5mm) chains on my bench - just thought I'd let you fellow engine tinkerer's know. Nick S."

One thing I learnt in the long long ago past is that repeated camchain issues are pretty much always a dodgy tensioner. Not heard of this being a regular issue on the trx's but certain models are fraught with problems - early SV650's, any VF/VT series honda etc.

While you have the automatic tensioner out have you inspected it?

Dirty Trix - I have wound the motor over several times after putting the tensioner back in, (spark plugs out) and there is no obvious contact going on there. then again, it's the inlet cam and it appears to be retarded about 3 teeth... afaik the piston won't be near TDC while the inlet is open (when it's retarded) so i'd be most suprised if there was contact there. might be a different story if it was advanced though right?

And the whole point of the operation was to remove and check the tensioner, that's the only reason i started on any of this, so i've inspected the tensioner, and so far as i can tell it's alright, my mechanic mate said it'd be almost impossible to acctually see any damage to the teeth, it'd be a matter of finding which tooth it was sitting on and giving it a firm belt with a hammer to see if it slips...

Hans J - That looks VERY useful... where did you get that? Haynes manual? or somewhere else?

idl1975 - I had considered a new chain, but since the tensioner was only about 50% of it's full extent i didn't see this as being necessary...

the marks as described above must all line up , i fitted a new chain but the tensioner was ok , if the marks are retarded you will loose power , have you got 2 springs ? one goes inside the other on the tensioner

TRiXy wrote: ...
Hans J - That looks VERY useful... where did you get that? Haynes manual? or somewhere else?
...

Original Yamaha Workshop manual, better than Haynes, but still not 100%... I believe it's availabe for download frpm this site somewhere? If your chain is worn, both markings should be retarded by approx. the same, not just one => it has slipped at least one tooth...

Steve speed - Yup, got the 2 tensioners, still haven't touched the bike for a few days now, will get there and make sure it's all lined up.

HansJ - Yeah, i got that manual, but couldn't find those instructions...

Chapter 4, page 10-11. Sure You have the Workshop manual, not the owner's manual?