Yamaha TRX850 Enthusiasts Forum

Given the weather this weekend is really throwing it down..not bush fires now,-..now its floods...sheeesh;, decided to have a whack at fitting a cam chain myself.., normally id let the mechanic do this as there might be a trick to it, but armed with a workshop manual,a good set of tools, engine silicone and the new chain...decided to give it a go...fairing off..radiator out..thermostadt and upper coolant hoses off..[clean up mess]...drain upper oil tank then oil pumps out...cam cover off..cup of tea....
Now for the cam chain.tensioner and slides,.. remove and flip the chain over the sprockets , down to the crank and out the oil pump chamber...fit up reverse...as long as you dont turn the motor or the cam sprockets from their set place..you wil be right...otherwise - well .... .Anyway, thats it.

Total cost was for the chain which i already had thanks to a member 6 months ago..and having a scottish heritage,..i reused the cover gaskets.. after close inspection, i found that if i used more silicone, it would be tighter than a fishes bum.
A very clean straight off cam cover and NO recession to the valve clearances after 60.000 plus kays...good fuel and good oil.
Did i mention this engine dosent use oil either..?
Food for thought, i had a chain fettled to this motor around 60.000 ago and the tensioner was close to the limit this time around..not too bad for a cam chain, highway kays tho.

How long did it take ?

Thebroady wrote:How long did it take ?

Hi Broady, time was about 3 hours, and thats with the remove and replacement of the fairings, radiator with coolant, draining and filling the engine oil.
Essentially, after removing the cam cover, its bringing the motor to its Top Dead Centre firing stroke.[manual], remove the left side lower oil pump cover--then the two pumps [no tricks there]..remove the cam chain tensioner, and inner front chain slide..the chain goes slack now,so just lift the chain over the cam sprockets and drop it down to the crank and out the oil pump cavity...fit up reverse.
The motor is on TDC when the left cylinder inlet and exhaust cams are facing away from each other [see photos],..the top small plug on the alternator[once removed] shows a T mark...and the cam sprockets show the timing marks.
Turn the motor over slowly with a 19mm socket in the big alternator plug [crankshaft].
The only caution is that the right inlet cam is at the top of its lobe, so if you turn the inlet can a couple of degrees, it will spin over and youve got to wrestle it back, while muttering profanity..

excellent, I had though that one would be able to do it like that but had not tried it. Great to know and thanks for posting

alextrx850 wrote:

Thebroady wrote:How long did it take ?

Hi Broady, time was about 3 hours, and thats with the remove and replacement of the fairings, radiator with coolant, draining and filling the engine oil.
Essentially, after removing the cam cover, its bringing the motor to its Top Dead Centre firing stroke.[manual], remove the left side lower oil pump cover--then the two pumps [no tricks there]..remove the cam chain tensioner, and inner front chain slide..the chain goes slack now,so just lift the chain over the cam sprockets and drop it down to the crank and out the oil pump cavity...fit up reverse.
The motor is on TDC when the left cylinder inlet and exhaust cams are facing away from each other [see photos],..the top small plug on the alternator[once removed] shows a T mark...and the cam sprockets show the timing marks.
Turn the motor over slowly with a 19mm socket in the big alternator plug [crankshaft].
The only caution is that the right inlet cam is at the top of its lobe, so if you turn the inlet can a couple of degrees, it will spin over and youve got to wrestle it back, while muttering profanity..

I reckon a link of cable ties around the socket bar / rachet handle and up to an anchor point could be utilised to ensure a one man job is made a tad easier. I`m yet to do a TRX cam chain but will be this year.

60,000 from your previous chain fitted? And your tensioner was all the way out.. Do you know what type of chain ( genuine OEM yamaha or generic) they replaced it with??? Replaced my Original at 100,000 and still had 2 clicks left on the adjuster ....

30,000 miles would be considered about right for a cam chain replacement in most cases cobba.

60,000 k`s equates to 37,000 odd miles so that would be in keeping with the above.

The previous chain was fitted by a dealer, so cant be sure of its source..
Most small japanese cars these days will have the cam chains and run out for hundreds of thousands of kilometers being hydraulic adjusted, so thats food for thought,..however, while my motor wasnt overly noisy, its a lot quieter now.
I could have run the chain for another 10 or twenty thousand kays,..but for the $90 for the chain, a couple of hours and now armed with the knowledge that it was easier than i thought..

Did you measure how much against the new chain the old had stretched Alex just out of curiosity? I got another new OEM yamaha chain in amongst my spares here somewhere if you want to measure it to get an idea for future chain choice

So just for clarity ( I can be slow on the uptake!) did you reuse the oil pump cover, "O" ring seal on the oil feed pipe, oil pump gaskets, scavenge pump "O" ring seal & pump gear circlips that Granny Heynes and the official Yamaha manual recommend swopping out? Any leaks or problems now it is all buttoned up? Oddly enough I was going to the dealers tomorrow to order all the above but if its really optional then all is good.
How did the camchain guide on the inlet side look? Thats the one that the camchain tensioner pushes on. Be interesting to know as if that guide was worn then that could be the cause of the camchain tensioner not quelling rattle rather than the camchain stretching.

Cheers DFH

dfh wrote:So just for clarity ( I can be slow on the uptake!) did you reuse the oil pump cover, "O" ring seal on the oil feed pipe, oil pump gaskets, scavenge pump "O" ring seal & pump gear circlips that Granny Heynes and the official Yamaha manual recommend swopping out? Any leaks or problems now it is all buttoned up? Oddly enough I was going to the dealers tomorrow to order all the above but if its really optional then all is good.
How did the camchain guide on the inlet side look? Thats the one that the camchain tensioner pushes on. Be interesting to know as if that guide was worn then that could be the cause of the camchain tensioner not quelling rattle rather than the camchain stretching.

Cheers DFH

Hi DFH, reused the all and sundry..a little continuous swipe of engine gasket silicone sealer to the cam cover rubber gasket and was carefull in releasing oil pump covers to preserve those gaskets as well..
The rubber o rings had resistance when refitting and not a leak of oil or coolant at all...a lot of care in cleanliness goes a long way.
Handy to keep important bolts pressed into a piece of outlined cardboard so you know where they definitly go back..
The cam chain tensioner runs on the back of the chain and so is quite smooth, so very little wear there and the load is shared to such a big area anyway...just take close notice and the feel of a part as it comes away helps to put it back with confidence as well...my only possible concern was that the nylon oil pump gears seemed a little sloppy on the pump spline..[both the same ] tho...see how you go dfh

cobbadiggabuddyblooo wrote:Did you measure how much against the new chain the old had stretched Alex just out of curiosity? I got another new OEM yamaha chain in amongst my spares here somewhere if you want to measure it to get an idea for future chain choice

Ill take a photo of the length to the old chain this weekend Cobba..apperently the streach is measured in the arc [ banana shape ] sound right ?

alextrx850 wrote: Hi DFH, reused the all and sundry.....see how you go dfh

OK I chickened out & ordered all the gaskets, circlips & guff including cambox cover gasket from Pitmans here in Adelaide. Most was in stock at Pitmans & everything was in stock in Yamaha OZ. Total cost? $48.. Cheap & in stock tells me these bits are regular service items.
Inquired about both the camshaft sprockets & the camchain tensioner side guide, none were in stock anywhere in Oz & were over $130 per item. That tells me these bits are not regular service items...

Will start major service next weekend. Carb rebuild kits, camchain replacement, valve clearances. Hi ho hi ho

Cheers DFH

This photo will show the wear to the chain at or about 60,000 klms.
Both unseen ends are touching the edge of the alloy sheet.