2007 crf250r won't stop backfiring

well to start I haven't been on a 250f since 06 but I missed it so much that i picked up a 2007 for cheap. the previous owner ran race fuel in the bike(not sure what octane i think 110) well i ran that true the bike now im back on 93 pump gas and now it backfires like crazy. every time i ride and let off the gas its just a bunch of backfire. how can i make it stop. bike still runs great just back fires alot.

jetting, mine did the exact same thing, then i changed the jetting and there is hardly any backfiring, if any at all now.

i know this will sound stupid but how do i adjust the jetting. I'm good with tools just never messed with a crab before

come on guys help a brother out

Under the carb under the bowl. You can get to it from the 17mm drain plig with out removing the bowl as well. Follow the arrow labeled Pilot jet.


You un-screw it, like this.


It looks like this:


If it is popping when you decelerate you need a larger pilot. 07 with a stock cam you probably need a 72. The pilot size is etched on the pilot jet.

thanks. also what exhaust do u have on your 07?

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