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cr250 knocking any ideas?

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My 01 sounds the same but to me it sounds more like something external vibrating on the bike.  I haven't researched it in depth, though.  My 01 CR500 developed a similar noise last summer but it turned out the lower expansion chamber mount had broken and it was just vibrating.  Replaced the mount and the sound went away.

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My 04 sounds the same. I thought it's just the power valve?

definitely not the powervalve.  and that is excessive.  could be a lot of things like stated above.

whens the last time it was rebuilt in any way?

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I know for a fact, that those sliding powervalves on older 86-91, cr's had a tendency to wear, along with the guides, its possible with the older ones to have a piston strike! fire you bike up and ride it, if the noise gets worse then its time for a teardown!

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That is the actual video of my bike. I couldn't figure out how to upload it at first so I just used one that I found online that sounded the same

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When you revved the bike it didn't look like the power valve moved? When the bike is not running can you push the wing up and down?

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Pull the correct valve cover to expose the valve, give it some rpm s l o w l y, then increase it the valve should open at higher rpms, if it opens then that's not your problem, you know 2-strokes make lots of noise, you might be hearing rattling from the clutch meshing up to the gears, you might be hearing piston skirt rattle against the cylinder....could be a ton of normal sounds. As bikes get some time on them, parts loosen up with wear......

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I was going to tear mine down because I have the same noise but if you just did yours and that rattle is still there then I will wait. Was the noise there before the rebuild?

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When you revved the bike it didn't look like the power valve moved? When the bike is not running can you push the wing up and down?

 

 

Yes it moves freely

 

The power valve should have moved when you revved the engine, it did not. I would double check that you have it installed and hooked up/adjusted correctly. You can also pull the exhaust off and look at the piston to see if there are any signs of the valve making contact with the piston. That is a pretty good rattle that you have going on there and I would be hesitant to run it any further until you find out what is making all that noise.

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I just pulled my exhaust off and it looks like my power valve might be contacting the side of the piston. I have slight scratches on the exhaust side of the piston. I believe that while the bike is at an idle the piston catches the valves and makes them move up and down slightly causing the clicking sound. I think the RC valve shaft and valves are wore out. I can push up and down on them through the exhaust hole, they are pretty sloppy. Micah488 did you replace shaft and valves or just piston and rings?

Edited by lerea3

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