HELP!!!!!! 06 wr450 loud popping and flames on decel

Here is the way I think about it:

The piston goes down, intake valve is open and that creates a vacuum at the carb. This is why the engine sucks in air and gas. You open the throttle and in comes more air and gas. To first order, the vacum your engine makes has nothing to do with your exhaust because most of the time that the sucking is happneing, the exhuast valve is closed. Now, stricktly speaking there is a lot of fluid dynamics going on, some valve overlap, and your exhuast could have a small affect on the amount of vacuum created. Changes such as elevation and temp create a much bigger difference than changes to your exhuast.

I think this this explains why minor to moderate exhuast changes have little to do with your jetting. Now, if you changed your cams, or other parts of your engine you could imaging that you might need to re-jet because these would effect the vacuum generated durring the intake stroke.

"So if you change the the pipe eg: yz pipe, would you go up in jet size with the main? but just leave the pilot? also i just really noticed(just had a ride) when the engine is hot it doesn't like to keep idling"

go to the top of the forum and find the sticky about adjusting your fuel screw (pilot circut). You need to learn to do this or you will always be unhappy.

good luck, j-

I had the same problem on my 2005 model wrf-450.My jetting is 168 main 48 pilot.I tried everything but the bike wasn't perfect.Then i made the ACV mode and i unpluged the tps.End of popping for me and perfect idling..Totally different bike.Try it....

Your hotstart isn't hanging open slightly is it? This will definately cause the decel issues!!!

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