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Help me diagnose my rocker arm failure

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I recently bought a 97 XR650L. It was in good shape and had just under 10,000 miles on it. When I bought it there was a very slight tick in the top end. I just figured it was normal valve train noise for a honda. I changed the oil and filter as soon as i got it home. I have put around 500 miles on it and the tick has gotten progressively worse. Adjusted the valves and the exhaust were pretty loose. Only helped a little, but the noise continued to get worse. I decided to tear into it to see what was going on. The first thing I did was pull the down tube filter screen. It looked good. I then pulled the oil line off going to the head. It looked good as well. I then proceeded to pull the valve cover off. The left exhuast rocker was toast. It was concaved and missing about 1/8 of material. The lobe on the cam for that rocker was wore really bad. The rest of the cam looked fine as well as the other rockers. What would cause just one rocker to go? Maybe it wasn't hardened correctly at the factory.

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One possibility is that that valve was set incorrectly (way too tight) and it caused the wear. Another possibility is valve seat wear/failure. :smirk:

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I hope it wasn't valve seat failure. I didn't plan on pulling the head. The bike ran good. It didn't smoke and it started easily. I want to find a good used oem cam to put back in it. Some new rockers off ebay and see what happens. That should get me through the summer. If the parts look good after riding this summer then I will know that it was either ran low on oil at some time, or adjusted wrong. What would be the best way to check for a valve seat problem without pulling the head? A compression check? Could I do that with the valve cover off?

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i was wondering, if the top end had been opened up before, did all the arms and rocker arms go back together right? you'll notice if you have it apart, one rides the cam and intun pushes the other and then the valve, if one got put back in the opposite order, the arm will flap there. as careful as i was, i tried to set everything up, and when i was checking the clearances, i realized one was backwards, that one alone was real loose. if it went togther that way and then was ran, it may open the valve a bit but if it was in full operation, it could @$% some things up and make some noise...i would imagine. glad i caught mine!

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This is the typical failure from a lack of oil. Perhaps the previous owner ran it out and then sold it.

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This is the typical failure from a lack of oil. Perhaps the previous owner ran it out and then sold it.

With only one rocker and cam lobe failing? I guess it's possible, but you'd think that there would be at least some wear on the other rockers/lobes if it was oil starvation. :smirk:

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This is the typical failure from a lack of oil. Perhaps the previous owner ran it out and then sold it.

Plus 1#... I agree with cleonard, might have been run low on oil for a short while.

From what I've seen when this happens is the EX. lobe wears first and then if it was ran a long time they all get munched up.

Pop's

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