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:thumbsup: My 2006 wr 250 ran awsome one day and like crap the next. I am a certified mechanic, own 2 auto repair shops, know how 4 stroke engines work and I am baffeled! I bought the bike new from a dealer. Took it home and did the GTYR power up kit, removed all the air crap, did the grey wire, installede the Athena big bore kit(290cc).Installed the stage 1 intake and exhaust cam's from hot cam's. Replaced the stock pipe with a FMF Q pipe. After that, the bike ran awsome. I rode it all over southern Utah, huge power, could not even tell it from a 450cc, until 4th gear in the sand. next weekend I rode in Wyoming at high altitude (6500-7500) feet. At first I thought it was just running funy due to the altitude. It was hitting the rev limmeter at way lower rpm's and cutting out big time. Went home checked the jetting(drastic changes and it only affected it the way it should) not a jetting issue. I checked the valves, I did every check possible with the service manual,electrical and mechanical. Removed the carb completly and checked it again. put a meter on TPS, caught a glitch, replaced it with a new one from dealer. ran better but still not even close to how it ran before. It act's like the timing is off, but I have checked the cam timing and it is spot on. any suggestions? Please I am ready to push off a cliff and collect the insurance money.

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Check the fuel screw,Make sure it did not fall out. And make sure you have the fuel screw adjusted properly.

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I've been chasing a similar problem. Last Saturday I went on a high altitude ride 6k-9k and it ran fine. Got back looked at the plug and it was white so i raised the needle one clip. Sunday we go out again and it cuts out at mid throttle. I thought it was fouling a plug but it would clean up at full throttle so continued on. Been playing with the jetting ever since. Its a little better but still misses. I was thinking CDI too but hate to spend the money on a trial!

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To both of you, do the bikes start easy like they did before?

Cam gear might have slipped on cam. When dots are inline... are the cam lobes symmetrically opposed?

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Ignition timing and carburation mimic each other. Both of you need to check and make sure the Woodruff key in the flywheel has not sheared and let the flywheel slip some. If it has, then the timing is off. Usually if this happens, the timing get retarded and the motor will run hot.

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To both of you, do the bikes start easy like they did before?

Cam gear might have slipped on cam. When dots are inline... are the cam lobes symmetrically opposed?

Yep still starts fine. I do need to check the valves so maybe this week. Thanks.

Ronbuell: Woodruff key:

Yikes! Its amazing how it ran fine one day, park it, change the clip, ride it the next day and it misses. I need to get into this more. Thanks

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since you changed the clip, you probably needed to adjust the fuel screw some too. I'd put it back like it was before, then do a cleaning house to make sure the carb didn't have any dirt in it, then check the petcock and tank and clean those out. Also this time of year, water will condense out in the tank if you leave the bike outside at night. Modern fuel has just enough alcohol in it to mix with the water and cause problems. I alway run my carb dry or drain it out, and put fresh gas in the day of the ride.

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since you changed the clip, you probably needed to adjust the fuel screw some too. I'd put it back like it was before, then do a cleaning house to make sure the carb didn't have any dirt in it, then check the petcock and tank and clean those out. Also this time of year, water will condense out in the tank if you leave the bike outside at night. Modern fuel has just enough alcohol in it to mix with the water and cause problems. I alway run my carb dry or drain it out, and put fresh gas in the day of the ride.

Thanks Ron, agreed, the problem is I never seem to ride in the same temp or elevation especially this time of year. Oh well back to basics. Thanks again.

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Yea, we've seen it here too, although we don't have the kind of elevation changes you have. Temp changes wreak havok though. My buddy with his 450 has to dibble with the fuel screw during a ride to keep it from dieing. Now that the temps have come down, I'm cranking more fuel in too. Good luck.

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