fmf jetting for 426


6 replies to this topic
  • danomx69

Posted August 05, 2006 - 10:29 AM

#1

i just put on a fmf powercore silencer and a power bomb header....it ran fine untill i opened it up on the dirt...it was backfiring like crazy.....do i need to rejet it?..ive never jetted it b4 so i would not kow how to do it...is it dificult?...what would i need?..any help is appreciated..

  • ONLY4STROKES

Posted August 05, 2006 - 11:17 AM

#2

i just put on a fmf powercore silencer and a power bomb header....it ran fine untill i opened it up on the dirt...it was backfiring like crazy.....do i need to rejet it?..ive never jetted it b4 so i would not kow how to do it...is it dificult?...what would i need?..any help is appreciated..

How bad was it backfiring? On decel or acceleration? Did you use hi-temp silicone to seal it? Might be an exhaust leak.

  • 642MX

Posted August 05, 2006 - 03:13 PM

#3

Sounds like an exhaust leak to me. My bike didn't require any jetting changes when I got my FMF system (powerbomb header & Titanium 4 muffler), I do recall having to adjust my fuel screw a little bit though.

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  • danomx69

Posted August 05, 2006 - 04:52 PM

#4

it was backfiring on decel...its not leaking at all...its all sealed up

  • 642MX

Posted August 05, 2006 - 05:43 PM

#5

it was backfiring on decel...its not leaking at all...its all sealed up




Okay, so your lean. Back the fuel screw out 1/4 turn and try that.

  • barch88

Posted August 05, 2006 - 07:46 PM

#6

What size pilot jet are you running?

  • gbalias

Posted August 05, 2006 - 08:54 PM

#7

does the powerbomb header make any noticeable power with the stock silencer? ive got a 98 yz400 and i wanted to get one mainly so i didnt have to loosen it when changing the oil/filter. heheh..i know im a lazy fool!. but i really wasnt looking to get a power increase that was huge. my friend has the header on his 426 and it feels a lot more snappy compared to mine, but it might be like apples and oranges. his jetting didnt change either. nor do you have to move it to get to the oil filter.





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