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Odd yz250f high rev babbling issue

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Alright guys so I'm a bit stumped right now. We have my sister racing a mini sprint car (called an outlaw sprint) with an 09 yz250f motor in it. The motor runs great right up until it gets near the rev limiter where it sounds almost like it's flooding over and babbling like crazy. At that point it never really continues to climb in the revs and just ends up popping and babbling until you get out of the throttle. 

Some general info:

-It just had the top end rebuilt.

-14:1 piston, port work, runs on pure 110, fmf 4.1 with a megabomb. 

-Jetting is a bit rich when looking at a chart but it's close enough for now. 

-idles great and seems to rev just fine at a stand still with no load.

- under a load it seems to run really strong right up until the point as described above. 

 

I don't believe this is a jetting issue as just a few runs ago the motor never had this issue. Also, she pretty much has her foot buried to the floor (on the main jet) from the minute she gets half way through the corner and it isn't until the end of the straight that the motor starts babbling. 

Any thoughts or ideas would be great. cdi issue? Stator issue? Thanks!

 

pic of the car for fun. elliecar.JPG

Edited by iRidePhotos

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Not topic related, but at the dirt races were I'm from, the minis are all 270cc 2t motors. It would be cool to see a 4t mini tho!

I wish we were just running 2t's right now honestly! Went back to a smoker for moto and I forgot what a pain these things can be. But it's fun stuff!

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I wish we were just running 2t's right now honestly! Went back to a smoker for moto and I forgot what a pain these things can be. But it's fun stuff!

what size track are you guys going around?

Around me we got 1 within 5 miles, and 3 within 60. All race different nights. They all run 3/4 mile tracks.

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Have you tried just moving the needle a spot or 2. It could definitely be electrical (cracked or just bunk cdi that trips out when it gets a certain vibration to it. I've seen it happen more than once.) But I'd try just bumping the needle first since that's free.

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