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Cam Tensioner Spring Broken?

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2001 XR250R making a noise that sounds like the cam chain is slapping around in the cylinder. Started out on the quiet side, but if I start it up cold it seems quite loud. How often to the tensioner springs go, and how hard are they to replace if broken?

Also, what can I use for a new cam chain if needed? Will one fit off a CRF, or go OEM? And if I do have to pull the head off, is it a good time to do a BB or new valves? I still have lots of compression, no oil burning, valves have moved very little over that past three years.

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The tensioner spring has been known to break. Chances are, it's just a worn out chain, a broken spring can easily result in a chain derailment. Only way to find out what is going on is to remove the head cover and check out the tensioner. Look at the position of the wedges at the rear of the tensioner. If the rearmost wedge has sunk down completely in the tensioner body, the tensioner has reached its' max travel due to the chain being worn out. Pull up on the chain at the top of the cam gear. If the chain moves off the gear at all, the chain is shot.

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So I finally got the head cover pulled off today, and the tensioner spring is fully intact, the rear wedge is sunk down fully, and the cam chain can be lifted off the sprocket about a 1/16th pf a inch. Seeing this, I'd say the chain is shot.

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So seeing that the chain is shot, what's the best way of replacing it without ripping the whole engine apart? And if tearing the engine down is required, is investing in a BB a good thing to do at the same time?

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Yes, I got a PDF one.

So, remove the head cover, cam shaft, the clutch, oil pump, primary drive gear, change the chain, and re-assemble. Sounds like fun. Any specific tools that I will need, or any gaskets? And can I draw the chain up through the cylinder, or will it have to be removed?

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The manual specifies a clutch holding tool to remove the retaining nut. Easiest way is to use an impact wrench. You will need a new side cover gasket. No need to remove the cylinder or head to remove/install the chain, it will go out and in through the top. Pay close attention when you remove the side cover, clutch, oil pump and primary drive gear and associated components so that you can reassemble everything correctly.

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