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Yz250f makes a popcorn like sound rolling downhill?

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My yz250f when trail riding coming down a steep hill usually in 1st makes a popcorn like popping noise from the exhaust. It doesn't really sound like backfires but it just pops several times in a row a few times like pop pop... Pop......pop... Pop pop pop. Just wondering what this is? Maybe not enough air with the jetting? Or bad exhaust packing? Idk

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Lots of reasons but if it's all stock and everything's buttoned up good it's more than likely your fuel screw/jetting/mapping which ever one you have. Most bikes come lean from factory. Need more fuel.

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Lots of reasons but if it's all stock and everything's buttoned up good it's more than likely your fuel screw/jetting/mapping which ever one you have. Most bikes come lean from factory. Need more fuel.

well I'm thinking of taking the baffle/spark arrestor out so if I did (jetting is stock btw) would I need a rejet or no?

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Some popping is normal. Just pilot circuit slightly lean on decel. But it means your bike will start easier hot. Very fine line. If it seems to pop too much just turn fuel screw out 1/4 turn.

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Some popping is normal. Just pilot circuit slightly lean on decel. But it means your bike will start easier hot. Very fine line. If it seems to pop too much just turn fuel screw out 1/4 turn.

where is the fuel screw and 1/4 turn left or right if you're looking directly at the head of it?

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At the bottom of the carb intake side, looking straight at it cw is lean ccw is rich. With stock screw it is really hard to get in there and turn it. Also going up one on pilot jet wouldn't hurt either.

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At the bottom of the carb intake side, looking straight at it cw is lean ccw is rich. With stock screw it is really hard to get in there and turn it. Also going up one on pilot jet wouldn't hurt either.

so looking at the carb on the left or right side? And turn it 1/4 out ccw.. Btw if I do take my baffle/spark arrestor out would it need a rejet if its lean?

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ImageUploadedByThumper Talk1407606292.332374.jpg

White arrow. CCW for rich. I don't think it's necessary to rejet but if your taking your carb off I would go up one on pilot and buy a adjustable, billet fuel screwImageUploadedByThumper Talk1407606439.480636.jpg

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check for air leaks from your exhast or it could be your jetting is to lean they are the most likly reasons

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If your needle and seat is worn it will also do that its called gargling (like when you brush your teeth), easy to diagnose tho when it does it just accelerate slightly, if it revs out until you back off or the bike speeds up then its probably worn but will do it in any gear not just 1st

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if you have aftermarket fuel screw its on the bottom of your carb in the float bowl, usually colored and numbered, just turn it out to let more fuel in.  If you don't have one buy one, there 20 bucks and these carbs can be a bit tricky so its worth it.

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ALSO! Something else came up.. Kindof like a ticking noice/clanking noise coming from the mid year and sometimes a noise like im dragging a stick but that's possibly the chain... It needs tightening. But the clanking noise im pretty sure is the sprocket.. The teeth are getting small so it's hitting the bottom of the chain and I can see the front sprocket wearing out a little, was just wondering what this noise could be.

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