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07 rmz450 backfire on decel?

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i just bought an 07 rmz450 and the guy says it has about 5 hours on it.. he said its been sitting for almost a year. i believe him kuz its clean as hell and everything. wen i accelerate it seems awsome and what not but wen i let off the throttle it backfires like a mother.. plz help i dont wana wreck my new bike.. this is my first 4 stroker. thank you:excuseme:

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well i see your from WI. so am I. my 07 does that on decel too, in this weather! its just running lean because its so f'in cold out. wait till its 50 or warmer out and she will be runnin fine! mine runs perfect in the summer , then this winter on the ice it would run supper lean! if your gunna ride in the winter it should be re-jettd.

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The most likely cause is not having an air tight joint where the exhaust goes into the head, if the bike has only 5 hours the joint may well of settled in and just need to be retightened, or may need a new sealing washer. Next thing to look at if that's not it, is the mixture, usually too lean although I believe it can also happen if too rich. You will need to swivel the carb round to easily access the mixture screw which is underneath, a good starting point is 1 3/4 turns out from fully in.

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its just runnin lean because of the cold weather it is set from the factory to be run in 80 degree weather or close to it you know what i mean-summer- anyway it isnt the best thing for the bike. any mechanic will tell you to rejet it if your gunna ride it in the cold. but to each his own i guess. i know guys that run um lean in the winter cus they are to lazy to rejet and i know guys that just rejet.

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Check your intake manifold mine had the same symptoms seemed like it was lean. I went to replace the pilot jet only to notice a little play in the manifold. Sure enough it was cracked. Got a new one on order hope it fixes it.

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