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c9buff

New pipe, Now popping

12 posts in this topic

05 WR 450 I pulled the stock pipe off and mounted a YZ slip on. When I rev the engine, as the rpm comes down the pipe starts to pop. This is done with the bike in neutral and not moving. Can't trail test it because of a foot of ice and snow outside.

Is this normal or do I have to worry about it?

Thanks,

buff

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Lean jetting or an exhaust leak. If your jetting is to lean it could be compounded by the cold weather. You may be alright once it warms up.

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When going from a muffler to a more open pipe, popping that was absorbed by the muffler is able to now escape. By changing the muffler to a more open one, you should of installed a larger main jet too. To deal with the popping, you can try opening the fuel screw (no more than three turns from gently closed). If that does not help, then a different needle may be needed. You cannot simply move the clip. You will have to go one size richer (thinner) on the needle straight diameter.

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Does the 05 have the AIS on there, and have you removed it if so? When you put an unrestrictive exhaust on a bike with AIS, then you are really going to hear all that crazy popping even with good jetting.

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Does the 05 have the AIS on there, and have you removed it if so? When you put an unrestrictive exhaust on a bike with AIS, then you are really going to hear all that crazy popping even with good jetting.

+1 When i put an aftermarket exhaust on my 07 it popped like crazy, then i removed the AIS and its A LOT better now.

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you may need to go up one size on the pilot jet aswell

YES and adjust the fuel screw accordingly

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Do a search on backfire and popping in this forum. Tons of info including a few of my threads as I went through the same thing last year and finally got it solved this weekend.

I tried all pilot sizes 42,45,48etc, different needles, main jets, pipe clamp on the new WB E2 etc, siliconing every thing that could possibly be an air leak, checking for air leaks with brake cleaner etc... Nothing worked. Except I finally replaced the last piece of the puzzle... the exhaust port header gasket. Voila. Now, my bike is actually running rich, so have to lean out my pilot. Its starting, idling and running smooth unlike before.

The point is... before with the stock pipe, the popping is less pronouced due to a longer pipe and more baffles. When you open her up, its pretty much a straight pipe and leaner to boot.

Just another thing for you to try if everything else fails. It took me 10 mins to change the gasket. I'm kicking myself for not doing it sooner.

Good luck.

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you may need to go up one size on the pilot jet aswell

Maybe two sizes, but definitely richer on the pilot. I did on mine.

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