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backfire on decel.. STILL
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Posted by: f150mann

i put on a hmf slip on pipe.. i started with a 155 main and stock pilot, it backfired on decel, and it was a little lean, plus was a little white, so i bumped up to a 158 main, and put in a 42 pilot, now it STILL backfires.. i have the fuel screw 2.5 turns out, ppl whats going on???? why am i backfiring.

also, it was just a slip on, so its not an exhaust leak. im furstrated, what do i try now?

Posted by: 250x_kyle

back fire on decel means your lean. call justin at jna racing he should be able to help you out (302) 750 0039

Posted by: dariusld

Did you try tightening your header bolts and see if that made any differrence?

Posted by: f150mann

no, as i never loosened them, and it only started backfiring once i put the slip on on, so its something to do with that. theres no leak on the motor

would a small leak at the pipe meeting the header make it backfire?

Posted by: CarGuy7a

yes it would. mine was leaking and it made it pop and such.

find yourself a stainless T-bolt clamp.

also it might be worth it to take the headers off and put new exhaust gaskets on it. even if it doesn't sound like it's leaking it still can leak enough to make it pop. i had the same thing happen to me.

Posted by: f150mann

i will try taking the pipe off, putting on some high temp silicone, putting it back on then tightening the crap out of it

Posted by: GPracer2500

quote:
Originally posted by f150mann
i will try taking the pipe off, putting on some high temp silicone, putting it back on then tightening the crap out of it

Get new header gaskets if you take the header off. Your Honda dealer is likely to have them in stock (the same gaskets are used on a whole bunch of different Honda ATV's/MC's).

Posted by: EX LONERIDER

given you will still have some backfire popping... when decelerating you cut air flow... thing is you may have too much fuel and thats just the unburned fuel popping in the header.

also, how bad a backfire we talking about? constantly? here and there during decel?

Posted by: f150mann

seems to be on the bottom end of the revs when im slowing down, quite loud crisp pops

Posted by: maxamillion

Once you stop accelerating and let off the throttle a strong vacuum is created through the intake and into the combustin chamber. This lean condition and high vacuum carries unburned fuel particles into the exhaust. These particles then combine w/ hydrocarbons which causes detonation inside the exhaust and therefor backfires. I would check for airleaks around where the intake manifold(rubber boot) connects to the head. It could have been backfiring slightly before you installed the HMF and now it is just loud enough for you to here it easily.

Posted by: EX LONERIDER

basically what he said ^^^

quote:
Originally posted by f150mann
seems to be on the bottom end of the revs when im slowing down, quite loud crisp pops

down low its pretty normal but im not sure if your pipe just amplifies it... the only thing i could think of at low rpm is header gaskets.

Posted by: f150mann

well i put some heat silicone on the slip one and tightened the sh*t out of it, def no leak now.

and yet..still backfiring like crazy, i ordered a new header gaskets for it and will install those when it comes, but i never had it removed so im 99% sure that isnt it. anyone have any more suggestions?

Posted by: 86 Quad R

make yaself a stethoscope using a hose. have one end of the hose to your ear and the other at the joints in question and someone blip the throttle. if there is a leak you'll hear it for sure.

Posted by: 450rJam

try putting the air box lid on ? easy way to see if its jetting, if it changes for better or worse.

did you use a new plug for your plug chop ?

im leaning towards exhaust leak also
(did let it set overnight to let the high temp set up?)

Posted by: f150mann

yea the silicone was very dryed, and i put a new plug in and rode tonight for a while, ill pull it tomorrow and see how it looks.

it feels like everything is right, except for all the backfire.

Posted by: 450rJam

to get a true plug read you cant "ride for a while" here is how I was taught to do a plug chop

1. warm up motor
2. change plug (dont get burned)
3. start it up and take off as if you where drag racing
(through top gear, then pull in the clutch and kill it/coast to a stop)
4. remove plug to check, there will be a ring around the base of the porcelain (sometimes you have to cut the threaded part to see it clearly)
a nice caramel color is what your trying for.

you want to see what its doing at w.o.t. where the main jet is being used.