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XR100 has noisey engine

By Frank ZX,
in XR/CRF80-200

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Frank ZX

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I just got a new to me 2002 XR100.The top end is pretty noisey.I took the valve cover off last night and rolled the engine over by hand,and it sounds like the rocker arms are slapping the cam making the noise?

I adjusted the cam chain and valves,and it still makes the noise.

Has any of you XR guru's had this problem?Please help,I have been into several XR engines,but have never heard of this.

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Racer

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I just got a new to me 2002 XR100.The top end is pretty noisey.I took the valve cover off last night and rolled the engine over by hand,and it sounds like the rocker arms are slapping the cam making the noise?

I adjusted the cam chain and valves,and it still makes the noise.

Has any of you XR guru's had this problem?Please help,I have been into several XR engines,but have never heard of this.

What clearance did you adjust the valves to? Did you put the piston to TDC on the compression stroke when setting valve clearance?

Did the noise change when you were adjusting the cam chain? Is the chain now tight or did you run out of adjustment and it's still loose?

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Frank ZX

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I set the valves .002 intake and exhaust,engine at room temp,and both valves closed at TDC.

I adjusted the valves on tons of Honda engines.I think the problem is something else.

BTW,The bike starts on the first kick,and runs great.Just noisey.

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Frank ZX

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Piston slap?

I don't think so,but it could be.It is a very unusual noise.I have had many bikes in my 38 years,and rebuilt a few bike engines,but this noise has me stumped.I guess I'll let the kids and wife ride it and see what happends.If it lets loose,I'll get a 120 or 132cc kit.If any:ride: body has any answers please let me know.

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Racer

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I adjusted the cam chain.Do you think I need a new chain?
Possibly, which is why I had asked in post #3 if the sound changed at all when you were adjusting the cam chain. Quick question, when you adjusted the chain did you SRART the engine, then loosen the nut (its just a lock nut) then loosen the screw which releases the inner spring loaded adjuster, allowing it to tighten the cam chain? After about 5 seconds tighten the center screw and then tighten the lock nut?

I'm guessing that this is what you would have done being that you are indeed familier with these engines but just thought I'd better check just incase so there is no confusion. :ride: If this doesn't/didn't help then I would suspect you need a new cam chain.

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Korbenw7p3c

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...I don't have a manual yet, but are you 90% sure that the cam chain is adjusted WHILE the bike running? Thought I'd give a try to the method you described and see if the noise quit. Where is the location of the cam chain screw/locking nut on the CRF100?

Thanks...

Possibly, which is why I had asked in post #3 if the sound changed at all when you were adjusting the cam chain. Quick question, when you adjusted the chain did you SRART the engine, then loosen the nut (its just a lock nut) then loosen the screw which releases the inner spring loaded adjuster, allowing it to tighten the cam chain? After about 5 seconds tighten the center screw and then tighten the lock nut?

I'm guessing that this is what you would have done being that you are indeed familier with these engines but just thought I'd better check just incase so there is no confusion. :ride: If this doesn't/didn't help then I would suspect you need a new cam chain.

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socalxr

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You should be able to feel pressure against the adjuster if the cam chain isn't stretched. If there's no pressure or if the noise doesn't quiet down with a 180 degree turn, then it's time for a cam chain, because it will rub against the cylinder wall and you will have aluminum in your oil.

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Frank ZX

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Possibly, which is why I had asked in post #3 if the sound changed at all when you were adjusting the cam chain. Quick question, when you adjusted the chain did you SRART the engine, then loosen the nut (its just a lock nut) then loosen the screw which releases the inner spring loaded adjuster, allowing it to tighten the cam chain? After about 5 seconds tighten the center screw and then tighten the lock nut?

I'm guessing that this is what you would have done being that you are indeed familier with these engines but just thought I'd better check just incase so there is no confusion. :ride: If this doesn't/didn't help then I would suspect you need a new cam chain.

I loosened the jam nut,and let the screw turn by it's self.Also,the screw on the back of the cylinder,I slide the rail up slightly.

Would you tell me the correct way to adjust the chain?

I'm starting to doubt the way I adjusted the chain.Thank you so much for your time.

Frank

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Racer

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This should help you Frank ZX:

https://www.thumpertalk.com/forum/showthread.php?p=7879235#post7879235

The upper bolt is eccentric, when you turn it it bows the tensioner against the chain, just turn it gently until the noise goes away. The lower bolt on the back of the cylinder holds the bottom of the tensioner. Loosening it allows a spring to pull on the bottom of the tensioner. I prefer to have the engine running when adjusting the lower adjuster as well.

Hope that helps!

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BOULMAN

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I bought a motor off ebay and it ran good for a while and then started knocking. Come to find out the nut holding the rotor on was loose causing it to be very loud. Always ran good.

Something to try. Just pull the left case cover and check the nut tightness.

JB

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Frank ZX

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Like I said before if the eccentric just turns easy with no resistance, you need a new cam chain. You could just buy a base and head gasket and pull it apart just to give you piece of mind.

I did feel resistance when I turned the adjuster,but no change in the sound of the engine.

I have noticed the engine being extremely cold natured,and running at high idle.I know this sounds like carb problems,but I wonder if it has something to do with the engine noise?

I guess I will have to tare the engine down to see what's wrong.

The last XR100 I had bent a valve some how,but it made no noise,it was just hard to start,and edventually blowing compression into the crankcase.I replaced the exhaust valve,and it ran fine.

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