01 yzf426 w/ fmf Q jetting or tuning help?

28 replies to this topic
  • Brandon Meidam

Posted December 23, 2004 - 10:31 PM


Hello John,
I never had the bog with the white brothers E series exhaust which had 18 disks. As soon as I put the FMF Q on the bike started to bog on the bottom end and run real rich. I have purchased a 40 pilot and may try to move the needle down but just haven't had a chance to try it yet. I may look into these other mods if I can't get the bog out this way. Thanks for the info.


  • Brandon Meidam

Posted December 23, 2004 - 10:36 PM


Hello again Brandon V,
By the way, nice name. How much did the 450 diaphram run you ? I have been recomended to try the 40 pilot over the stock 42 and then move the needle to see what happens. As soon as I get a chance to ride the dam thing I will know if I need the diaphram or any other carb mods. It ran great until I put that FMF Q on and now it runs like crap. Are you running a FMF Q on your bike?

Brandon M.

  • Guest_BrandonV_*

Posted December 24, 2004 - 06:08 AM


Nice name yourself :cry: There's a few Brandon's arouns here now, we're taking over!

I've got a DSP titanium exhaust which is less restrictive than the Q as its a closed course exhaust. Also, I can verify that I run a #40PJ, 158 main, OBEJP needle in the #3 pos. and 1.5 - 2 turns on the screw depending on alt. The bike runs like a raped ape....
If you feel like making the trek to the Gorman/Frasier Park area next time we go you're more than welcome to ride it, plus you can try out the 14/50 gear combo :cry:

The 450 diaphram is around $10-15, cant remember exactly but I felt it was worth not having to drill & tap a screw into the carb.

I'm off to Vegas, please let us know how it goes so I can see when I get back. Later!

  • Guest_BrandonV_*

Posted December 27, 2004 - 10:50 AM


So what happened?!?!?!

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  • yzwiley

Posted December 27, 2004 - 07:28 PM


Brandon M, if you are in Paso go see Huft Daddy at Powerhouse. He can set you up with the different accelerator pump diaphrams. It's not just a YZ450 thing, but is also available for your 426. Yamaha simply sells optional parts for the diaphams; leaner to richer.

I doubt the accelerator pump is your problem. I'd start with the pilot jet and work if from there.

Also, the position of the needle will give you a bog too if not in the correct position.

  • CRFThumper

Posted December 28, 2004 - 05:57 AM


I would bet (although :cry: not to much) its the needle!Let us know what you find out!

  • Brandon Meidam

Posted December 28, 2004 - 10:29 AM


I am planning to try some of these tips out on Friday and Saturday. All my family will be leaving by then (thank god). Hopefully the rain lets up so I can ride the thing this weekend. I will post my results.

  • Brandon Meidam

Posted January 02, 2005 - 07:04 PM


Hello everyone,
I just wanted to thank you all for the help with my sick bike. I cleaned out the carb with carb cleaner, installed the 40 pilot jet , dropped the needle down one notch (#3), installed the 03 YZ450 accelerator pump diaphram, and topped it off with the ZIP/TY adjustable fuel screw set at 1 and 1/2 turns out. This thing is so crisp and responsive now! I also dropped my gearing back to stock and it's like ridding a different bike that is way more responsive from idle all the way to wide open throttle. Nice cheap power improvement without the guesswork. Thank's again,

Brandon and a happy 01 YZ426

  • Guest_BrandonV_*

Posted January 03, 2005 - 10:11 AM


Nice dude :cry:

Those tweaks made a world of difference on my bike too. I know there's a few more ponies I can squeeze out of there with some more tuning, but I've been wanting to ride more than tune lately. Give me a shout if you ever want to ride down here..... Los Padres Nat'l Forrest is only about 2 hrs from you.

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