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Stretched Cam Chain

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I've got a XR100 (in a CR80 frame) with TB132. The engine has been making a loud ticking noise lately. It's also been losing power somewhat, especially when warm.

I checked the valve clearance and tensioned the cam chain. No difference.

I went ahead and pulled the head and cylinder off. The rod is tight on both ends. The piston doesn't seem to have excessive wear (compression was good too.) I put it back together and it's making the same noise.

I did notice that the cam chain is quite stretched. The upper cam sprocket is a few degrees off from where it should be as a result. Could my stretched cam chain be my entire problem?

- Brad

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My son has an xr80 and I recently had the same problem. I thought the chain was tensioned properly and did what you did. Turns out that I was measuring the valve clearances at TDC but not on the compression stroke. I am kind of new to 4 strokes so I'd thouht that TDC was all that was needed. Made the correct adjustment and kablammo, no more ticking!

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On the cam chain adjustment, Ive had the best luck with this method, Turn the upper adjuster untill the small punch mark is at 12:00 then tighten clamp bolt. start the motor and let idle, loosen the lower lock nut and lower adjuster screw while the motors idling then tighten the adjuster and lock nut. now you can fine tune the upper adjuster untill the chain noise is gone, clockwise to tighten, counter clockwise to loosen. If this doesnt work the chain has streched too much, good luck.

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Thanks for the responses.

I haven't tried adjusting the lower with the engine running, but did it with the engine stopped. The upper adjuster seems to have very little effect, probably because my timing chain is too stretched.

I shortened a XR200 cam chain that I had. I'm waiting for a flywheel puller tool to arrive and I'll swap it out.

- Brad

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I installed the new timing chain today. It's nice and tight and the timing is now correct, but the motor still makes a loud ticking noise.

While I was in there, I noticed that I had a fair amount of vertical play between the cam and the journals. Could this make a ticking noise?

Otherwise, I think the only other thing it could be is that the piston's getting too loose in the cylinder. Is this a common TB132 problem?

- Brad

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