A forum for owners of Yamaha TTR250 trail and enduro bikes!

any body know a good supplier for a timing chain for a 4gy.

thanks

keith.

wow thanks dont suppose you have any phone numbers do you .

keith

Moto Ward

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If a cam chain is very worn then the horizontal lines on the cam gears won't line up as they should do. I have only got a photo of the gears with a good chain - sorry!

If the adjuster is fully out and not taking up the cam chain slack then you would be able to feel this by pressing on the chain between the cam gears. It should be really tight - any looseness here would be bad news.

Cam chains are cheap enough but a fiddle to fit as they don't have an owner-friendly split link 

Brian

alan wrote:

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Thanks for your reply. Hard to explain, as you accelerate what i can only describe as a chain noise is very noticeable, if you feather the thorttle the noise stutters, when you close the throttle the noise stops. regards Alan

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It has been known for the drive chain noise to sound like it is coming from the engine.

Check your chain is adjusted and lubed properly and that the upper roller bearing is OK and not falling apart coz that can make a racket. Also check the sprockets are aligned - usually it is sufficient that the snail cams on the rear axle are on the same spot each side.

Also check your chain slider isn't worn through which would allow the chain to make metal-to-metal contact with the swing arm bearing cap. Just an idea...

Brian 

I stripped the clutch out on my 325 whilst the engine is out and it was only a few extra bolts to undo to get the timing chain off to check so I did so!

It is difficult to gauge chain wear but a simple check is to hang the old chain alongside a new one and compare their length. You can see from the pic below that the old chain at the back has stretched and is hanging lower. So I am putting in a new chain!

Not very scientific I know

Brian

ttr steve wrote:

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Hi

I am new to the forum, so hello to you all.

Anyway I have been checking my valve clearances and while doing so noticed that the inside of the  cam cover had a little bit of wear, just above the cam chain. This made me have a look at the cam chain, I can move it up and down a good 15mm, between the cam gears. I had a look on this forum to get some advice and show you my picture of my cam gear alignment. My question is this, how do I know if it is the tensioner or the cam chain? or will I need to replace both?

Cheers for advice. The pictures are a bit out of focus, need a new camera as well

Steve

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Hi Steve

If the crankshaft was definitely at TDC when you took those pics then my initial observation was that your cam chain is toast mate! Not seen one that worn before - unless the chain has jumped a tooth on the sprocket   

It's not clear from the pics so can you advise - is the LH sprocket line tilted over more than the RH sprocket (indicating a worn chain) or are they exactly parallel (more likely the chain has jumped a tooth)?

Brian

Hi Jarrah and Brian

Thanks for the advice.. Yes the tdc is correct, I checked it 3 times, it has not jumped a tooth, as if you put it back a tooth it is out the other way. The left hand one is slightly more out of line.

So I agree with both of you, a new chain is needed and I will check the tensioner.

Will the clearances on the valves change when I do this???

Or is it ok to carry on with this part of the work.

Many thanks

Steve