Jetting change needed with a Fmf Slip on?

2 replies to this topic
  • Nalgene

Posted February 01, 2006 - 08:54 PM


05 450yz ( Stock jetting, lil above sea level )
Just looking for imput on ppl that might have done just a slip on upgrade. Did you need to change your jetting at all? I am happy to hear my decel popping sound is gone. I had figured there was a leak in my exhaust *took a nasty fall and bent it up, must of missed a crack when I patched it up using JB Weld*

I would read the plug but damn if it inst a pain in the ass to do quickly.

Thanks for the responses ahead of time.

Visit the ThumperTalk Store for the lowest prices on motorcycle / ATV parts and accessories - Guaranteed
  • snowboardstylee

Posted February 02, 2006 - 12:04 PM


I can totally tackle this one ......

i have a 04 YZ 450 im about 1200 feet above sea level and put a Titanium FMF factory 4 on it. just the slip on(mid pipe and muffler) , didnt notice much change at all but a little decel popping going on. I had talked to the guys at FMF to see what they recommended for jetting, they said its listed on their web site. so .. i go to their web site. and it says with that muffler to run a 165 Main jet and a 42 pilot and use the stock needle on teh 3rd clip position.

WELL that is the STOCK settings. what a bunch of bone heads the 2004 and 2005 both came factory with a 165 main and the 2004 had a 42 pilot jet and the 2005 a 45 pilot jet.(yamaha web site)
I changed my pilot jet to a 45 and have 2 turns out on the Fuel mix screw and put in a 168 main jet and the decel popping is gone and the bike SCREAMS. I put in a 170 just to see if there was any difference and there wasn't so i kept the 168 in this should work for you .

DO NOT order the FMF power up or Dinojet jet kit its USELESS by the way. and you have to use this stupid main jet adapter cuase there putting small round jets in it with hex adapter. just go to your local cycle shop and get the Keihin mains for 4 bucks each .

  • Nalgene

Posted February 02, 2006 - 04:55 PM


WERD!! thanks bro.. you hit my question right on the head.. Kudos.. :thumbsup:

I am on my way to pick up my 168 jet. later..

Related Content


Should I buy this bike? help....... by Numsa Hul

Dirt Bike   General Dirt Bike Forums   What bike should I buy?
  • * * * * *
  • 10 replies

Chubby dad, looking at bikes , First trip to the orange/black forum ! by Slow_ride

Dirt Bike   Make / Model Specific   KTM   250-530 EXC/MXC/SXC/XC-W/XCR-W (4-Strokes)
  • Hot  28 replies

2016 YZ450 by CaptainKnobby

Dirt Bike   Dirt Bike Technical Forums   Suspension
  • Hot  59 replies

Megabomb Fitment by 288yz450

Dirt Bike   Make / Model Specific   Yamaha   YZ 400/426/450
  • 1 reply

Wilson the Blue Privateer by jetfuel

Dirt Bike   Special Interest Forums   Pro Racing
  • Hot  50 replies

Join Our Community!

Even if you don't want to post, registered members get access to tools that make finding & following the good stuff easier.

If you enjoyed reading about "" here in the ThumperTalk archive, you'll LOVE our community. Come join ThumperTalk today!

The views and opinions expressed on this page are strictly those of the author, and have not been reviewed or approved by ThumperTalk.