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Old 08-02-2008, 02:17 PM
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Join Date: Aug 2008
Last Online: 08-02-2008 02:17 PM
Location: Georgetown
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Default 04 Yz250F bogging from idle

Ok. When the bike is idling and you rev it hard, it will bog out. If you rev the bike to about 2000 rpms and let up it will idle higher then you can rev it all you want.. then if you shift into first and let it move a little, it will drop in idle again.

If you mess with the valve and run the idle up and down there's almost no difference.

I have a FMF full exhaust with titanium header, K&N filter

I was running a 188 main jet, i moved to 195 main jet to see if it was just running to lean, but im not sure that was the problem.

running 195 main jet
72 pilot jet

I live in kentucky so that's kind of norm.

Any suggestions?
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Old 08-16-2008, 11:00 AM
Dano426's Avatar
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Join Date: May 2003
Last Online: 08-21-2012 06:01 AM
Location: Minnesota
Posts: 721
Default Re: 04 Yz250F bogging from idle

Sounds like you have two different issues.
1. hanging idle
2. low end bog

Tight valves are one of the cause for a hanging idle. Also play with the idle screw. A 1/8 turn will cause mine bikes idle to hang at times.

You will not want to adjust your main jet to fix your low end bog. Put the 188 main backing and get your self a smaller leak jet. #50 or #60 (I went with the 50)[Only registered and activated users can see links. ] To help fix the bog, take a look at the o-ring mod.
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Old 08-17-2008, 08:50 AM
Semper Fidelis
Join Date: Dec 2002
Last Online: 02-26-2014 07:31 AM
Location: Barrineau Park, FL
Posts: 7,291
Usflag Re: 04 Yz250F bogging from idle

Dano's advice is spot on. You should look at the GMB/BK modification to the timing of the accelerator pump that Bryan Kenney and Garrett Berg perfected for the Keihin FCR carburetors. Best of luck.

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