Yamaha TRX850 Enthusiasts Forum

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.

i am so glad you brought this up,, i have been pondering more than just a little over this very problem ,,,i have come to the conclusion it just not worth the risk leaving the old one in ,,i plan to do a top end rebuild this winter and ive seen them priced at £50 in bitzforbikes which is round the corner from me the ones they sell are DID ,,is the std chain on the cheap side , what make is it ?,,, 5mm !!!!! i wonder how much that retards the timing ?

Tigcraft Tdm wrote: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.

As you´ve pointed out i changed mine....where 1,5 links stretched, struggled a long time before HansJ gave that tip...bugger!

What sort of Km's are we talking to get to that stage? Is the genuine parts Yamaha chain the go or after market? Brands?

devlin wrote:What sort of Km's are we talking to get to that stage? Is the genuine parts Yamaha chain the go or after market? Brands?

Mine was just shy of 40k km, used yamaha original part.

I've used genuine Yamaha, but will try DID next time -prob betterer quality! Also noticed that sprockets can wear on toothed faces - worth checking. I've also noticed that if you're cam bearings are well run in, and you turn the engine over with the rocker cover off, and then release the starter, you will see the chain raise on the exhaust cam sprocket as the valve train pushes the chain backwards. i.e you lose the tension between the sprockets, and it will get worse as the chain stretches. I had one engine where I was genuinely worried that chain would jump the sprockets at high revs. Also best to replace chain and sprockets as a set, to minimise wear on new chain, and achieve perfect timing.

^^^^^^^^^^^^ i hear what your saying and i will change both cam sprockets but we are fecked with the crank sprocket,,,, but this has to be better than leaving it to chance!!!

Tigcraft Tdm wrote: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.

Cheers for this Nick. I'm going to have my valve clearances checked and adjusted next month (not being as competent or as patient as you!) at my local shop, and will have them do the timing chain and sprockets as well. Don't want any exploding valvetrains on my commute.

Without wittering on 2 much, make sure they torque up correctly the sprocket nuts(24nm), and cam caps(10nm) as the threads are made out of cheese...(I assume the mechanic's competent there, I used to work as a Suzuki Spanner monkey,and I've seen some real shite supposed factory trained mechanics!!) You won't need to change the chain/sprockets if the marks line up, and the sprockets/chain appear OK. Nick.

fair point ,,so once the cam cover is off its a good idea to check the timing and if all the marks line up were good to go ,, if not is surgery time !!!

Errrm .... am I being dense here ? Surely if the marks line up all its saying is that the chain and sprockets are correctly fitted - it's no indicator of a stretched chain though eh? Your camchain can be properly shagged to the extent that the tensioner is next to ineffective yet the marks will still line up ....

I have to say though that camchains are easy to get complacent about and that mine, with my motor having done the best part of 44k miles now, is probably due for replacement even though it's not making noise.

Greg

If the chain is worn, and tensioner working correctly, the marks will not line up on the head. The exhaust sprocket (right one) will be below the head slightly, and the inlet (left one) will be above the head. Because the tension works only on the rear of the chain, the stretch at the front of the chain will cock up the timing. New chain req'd.

On the first engine that I built (approx 20,000 miles) the chain was absolutely fine but I replaced with OE item anyway and it still rattled like feck. The next engine had approx 14,000 miles and received a Tsubaki aftermarket chain even though the original was fine. (and still rattles like feck)

IIRC, Honks engine had over 50,000 kms when he tuned his and the cam chain was also fine.

I have not experienced any evidence of chain stretching but would recommend replacement anyway (makes sense for it to be done every 24,000 miles when the valve clearances are done).

Tigcraft Tdm wrote:Without wittering on 2 much, make sure they torque up correctly the sprocket nuts(24nm), and cam caps(10nm) as the threads are made out of cheese...(I assume the mechanic's competent there, I used to work as a Suzuki Spanner monkey,and I've seen some real shite supposed factory trained mechanics!!) You won't need to change the chain/sprockets if the marks line up, and the sprockets/chain appear OK. Nick.

Thanks for the tip!

Of course, as a former Suzuki spanner monkey, you're also probably aware that if you choose the wrong shop, they don't do the work but charge you anyway. Not to mention what sort of reaction you get as a punter if you tell the workshop counter blokey how to use a torque wrench, even if both of you know full well they wouldn't have done it correctly otherwise. Well, actually, I have a pretty good idea, having tried it a number of times in the past.

On that note, anyone have any suggestions for competent workshops within a reasonable distance from Guildford?

Didn't mean tell him to read his torque wrench settings book, think I was drinking when I typed that in! They'd love that wouldn't they, 'err excuse me Mr mechanic righty tighty lefty loosey'. Works for me anyhoose.