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 I've got a 2000 yz250 that runs real well for an old DT250. It starts easy and runs clean and then goes flat.

It has nearly 200psi of compression. The topend looks good with better than 50% of the original hone marks.

Piston looks great, and the powervalves work when operating  them by hand.

I am getting a lot of spooge going through the powervalve chamber. Have been through the carb with no changes.

Have not  changed the jetting because it ran fine before. The idle adjustment is unresponsive.

Also the bike revs high for a few seconds after I start it with the choke on. Any ideas?

l

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Probably not as interesting as graphics but I can add a troubleshoot point to the mix.

 The pin on the YPVS governor fell out. I don't know why or where it went, but all the other

parts are intact. I have a manual. Has this ever happened to anyone?

 BTW I'm very impressed with the power valve design on this bike, after dealing with an

"E" model KDX for several years.

 I am installing new rings and crank seals just because.

Edited by ventabular
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Check out my thread. "Mysyery pin broken pv linkage" I havent pulled it apart yet but I found a small pin on my drain plug which I beleive is from the governer

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Yeah, the choke lets through more air than just regular idle. So it'll rev higher. I just turn the choke off a couple seconds after the engine starts up.

You try new gas and a new plug? Also, my bike needs a good amount of warm up time before it'll run right on the top end. If you try to run it at way high rpms before warming it up, it'll seem like it just has no difference in anything past half throttle.

Edited by Thinlineggman

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Yeah its not unheard of. Glad you found it. Might be able to stick a magnet down there and catch it before it does any damage.

 

Revs out fine now, i take it?

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