2003 cr250 bogging on low end acceleration

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5/26/2021 7:11 PM

have a 2003 cr250r, had the bike for 3 years. run a airstriker carb, nedw 3rd clip,42 pilot, 172 main. been running this setup for years and never had an issue. new piston every year, and complete top and bottom rebuild last winter. we race motocross with it, ran 1st 3 races of the year and all ran well as usual. last race mid day the bike developed a hesitation on on acceleration, figured it was dirt in carb, took it apart cleaned it very well, hesitation was still there, re did carb cleaning and double checked float height and all was good, checked compression and it at 185psi.plug looks golden brown lie it always does, in in the lower to mid rpm range. checked needle and clip is still there and in same position we always have in it. kind of stumped. like i said we have ran the same jetting for 3 years and never had an issue. any ideas

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5/26/2021 7:49 PM

Check the RC valve servo motor. Take the powervalve cover off and make sure the powervalve is opening and closing correctly. The servo motors have been known to wear out and make the valve opening erratic. The geartrain in the servo motor assembly can also strip causing similar issues.

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5/29/2021 7:11 AM

checked the valves they are speratic at best, i see the servo for the 03 is not made any more, can i use one for an 05, the have different part numbers but look the same

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5/29/2021 7:36 AM

Sounds like you found the problem, I was going to suggest checking the reeds too

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5/29/2021 8:01 AM

Post a video of the PV operation. At start up, the valve will "dance" a little as it finds its end points but beyond that, it will follow engine RPM exactly. If it dances around during normal throttle openings, it's either a bad motor/geartrain or an extremely loose cable setup.

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5/29/2021 11:04 AM
Edited Date/Time: 5/29/2021 11:04 AM

thanks for all the repliies. dug in to the power valves and found a broken wire at the ecm. funny thing is i repaired this wire 2 years ago and was telling myself it cant be that, you fixed it last time. wonder why this wire keeps breaking off right at the connector. i extended the wire last time but it still broke right at the connector. anyone know where to get a replacement connector for the cdi?

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5/29/2021 11:09 AM

Try HERE. He has most OE connectors. I've been able to match everything I've needed on this site.

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5/29/2021 11:44 AM

Mr. Robinson wrote:

Try HERE. He has most OE connectors. I've been able to match everything I've needed on this site.

thanks, that's exactly what i was looking for

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5/31/2021 7:07 AM

Check where your cables run over the top of the ECU at full lock on the bars. It's very tight clearance in that area. I'll bet one of your cables (probably clutch) is mashing down on the ECU connector when you turn the bars to the left. Good luck with the fix.

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