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Old 03-19-2011, 09:54 PM   #1 (permalink)
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Default YFZ450 exhaust backfire????

I have a 2007 yfz 450 with a sparks pipe and we recently put a new piston,cylinder,and replaced the crank cases and i broke them in but about a week or so after we rebuilt it my friend was riding it and i noticed there was a short blue flame that popped out the back and right after that he went around a turn and the quad quit.i went to start it and a little fire came out the back but then it started right up and ran with no problems.that was about 2 weeks ago now and when i decelerate or even rev it up it pops real bad.bike runs good like it should just backfires like crazy.will this hurt it?wat can i try to do to fix it?any help would be much appreciated thanks
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Old 03-22-2011, 05:51 PM   #2 (permalink)
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did u jet it good? aftermarket pipes do backfire a lot so it could be normal.
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Old 03-22-2011, 08:43 PM   #3 (permalink)
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I installed an HMF full comp on my bike and it backfires. Like said above after market exhausts will back fire but if its really bad I would have your jetting checked out. If your jetting is off then that can cause it to backfire badly. When I first installed my pipe i only installed my pilot jet and I did it wrong, I had the same problem.
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Old 03-22-2011, 10:38 PM   #4 (permalink)
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did u jet it good? aftermarket pipes do backfire a lot so it could be normal.
im sorry im still learning about the yfz central and yea its jetted good but it puffs out some black smoke when the engines cold that means im running rich right?and also when i adjust my air fuel screw its right=leaner and left=richer right?
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Old 03-22-2011, 10:40 PM   #5 (permalink)
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Originally Posted by Smithjon View Post
I installed an HMF full comp on my bike and it backfires. Like said above after market exhausts will back fire but if its really bad I would have your jetting checked out. If your jetting is off then that can cause it to backfire badly. When I first installed my pipe i only installed my pilot jet and I did it wrong, I had the same problem.
ok because it runs normal i just was a little confused because it ran fine one day and then started popping the next day but i think its because i have an open core pipe.thanks everyone for the help though i appreciate it
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Old 03-24-2011, 04:57 PM   #6 (permalink)
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yeah left is richer as it opens the screw. could be puffing when cold from the choke maby or warming up still? that will make it rich.
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Old 03-24-2011, 05:08 PM   #7 (permalink)
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yeah left is richer as it opens the screw. could be puffing when cold from the choke maby or warming up still? that will make it rich.
yea because thats the only time it does it
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Old 03-25-2011, 12:58 PM   #8 (permalink)
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sounds like your jetted too rich
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