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So I've had my bike since may. Its an '04 636, used, had roughly 11,300 miles. The bike was taken care of as far as no scratched or cracks or major stuff. But I wasnt sure about how it was mechanically taken care of. It's my first bike, so no I didnt test ride it, but it sounded fine and everything and looked fine. So I did an oil change when I bought it just to make sure. I have put about 3,000 miles on it since then. I love it the thing is great. The other day I went ahead and changed the spark plugs myself...CR9E NGK is what I put in. Never knew if they had been changed before. But anyway, I was riding earlier and every once in a while when I would let of the throttle, it would "afterfire, or backfire." It never did this before, so If anyone would have any input as to what this might be, that would be greatly appreciated. Thanks guys...ride safe

Oh and like a dumb a**, the guy said the plugs were pregapped, but I never made sure before I put them in. Could this be it?

Thanks
 

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yes, usually the gap is a solid .7MM which i think is .020"

never hurts to check tho..

oh, and afterfire and backfire are actually drastically different..

one is a misfire typically caused by timing, and occurs in the intake or exhaust, and the other is firing after the engine is shut off.. (well, everyone has different definitions!! lol)


if it just started this, i really honestly (sadly) am not sure what to tell ya.. backfiring on bikes is pretty normal because of the aggressive timing and all they run.. the CR9E is the stock plug i'm pretty sure.. could try going up one heat range on the plug.. it shouldn't be ALL the time tho. .thats out-of-time cams or ignition or leaning out

might wanna actually check valve lash just for fun..

welcome to KF!!
 

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Maybe you just changed the way you're riding?
Giving hard throttle and then doing motor braking will cause backfiring at least with slip-on and no adjustments. Also declearing with the throttle just slightly open will cause it. Sometimes done that for the fun of it. :p
 

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heck mine has backfired since i own it and its been to the dyno to get tune several times, i just dont pay it no attention but i do like the sound when u are letting off the throttle and u hear that pop come from the pipe tho
 

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mine only pops when i'm running a strange home modded exhaust lol

the stock plugs are the cr8e aren't they? i'll check

edit: nope it's the 9E, theres nothing in the manual about backfiring. check the plug gap, and make sure the coil sticks are on good.
 

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dont worry about it mine does it all the time..sounds badass anyways like a gunshot.sometimes i do it purposely when passing punk ass kids on the street actin all hard and gangsta and watch them jump like girls.
 

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Make sure you did connect the intake sensor, and any hose that connects to the airbox. My NGKs have always been pregapped to .028 but i always make sure. If you dropped the spark plug in the spark plug well it could have change the gap. My money is on a bad reinstallation.
 

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got any kinds of mods on the bike? probably just running a little rich and its burning in your exhaust somewhere. my bike had an akra. slip on and a power commander map for an akra. full system when i got it. it backfired a lot. switched to a hindle full system and the map from power commander's web site for it. huge difference in power and just in the way it ran in general.
 

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yep slip ons will do it... once i put my slip on on it backedfired all the time then got pc3 all alot of it stoped but still does it some of the time
 
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