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06 CR250: Won't run on top.

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Hopefully someone here can point me in the right direction with my 06 CR250. Long story short: It ran great last Sept. on a weekend trip to Hatfield/McCoy. Come home clean bike and put away until another trip to H/M in Nov. It ran ok on the bottom, but if you nail it, it would fall on it's face. Sounds like it loads up and if I back off and get it lower in the RPM's it would clean out and run. Of course I pulled the carb and it was/is perfectly clean. Now I have installed a new plug, fresh gas... I was thinking the power valve wasn't working, but with the RC cover off, when you rev it,it dies out, but you can see the PV move. Also adjusted the slack in the PV cables. It has a boyesen rad valve, and the reeds look perfect. The pipe and carb are off, so I can see the piston and it looks good. PV in the cylinder is moving freely when I turn the arm that is behind the RC cover.

So basically it ran great one time, and the next it runs like crap. I didn't change anything with the set-up of the bike.

So if it's NOT the carb, power valve, reeds, plug, that leaves ingition. Bad coil? "Black Box"? I know it's getting spark, because it does run, but does it have some kind of ingition advancer built into it? Would a bad coil stop working as RPMs/vibration increase?

I've ridden bikes for 25+ years, and have always wrenched on my own stuff, but this one really has my stumped.

Any thoughts or suggestion would be greatly appreciated.

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My 04' did the same thing, it was my crank case seal. Is thier a lot of spooge? If your not losing any oil, go down on the main. What are the specs inthe carb now?

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Yea, there is alot of spooge. Looks like a 42 main and a 4? pilot.

I assume crank case seal is on the right side and you have to pull the side cover off?

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yea, the case behind the clutch cover. All you will need is a clutch hub holder, take the clutch out, and clutch basket. Its not behind it though, its to the right of it, behind a gear. You will see what i meen...

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I installed a 9oz. FFW when I got it. The top end looked good, crank seal was perfect. Now I'm thinking I spun the woodruff key, and it is slightly out of time. I ordered a new key, but can not install it until I get the new piston in the mail.

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my crank seal looked new, nothing wrong, but when i replaced it, the bike kicked in every gear, unlike before, when i would nail the throttle, it would bogg, not anymore.... replace it

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