1/2-3/4 throttle bog (tried but still looking)

3 replies to this topic
  • NuckingFuts

Posted December 15, 2005 - 04:29 PM


Ive heard folks say that bogging between 1/2 and 3/4 throttle can mean Rich or Lean. Help me understand what I have going on.

Bike Summary:
02 WR426
Stock pipe with Pro Moto baffle
YZ Timed & 03' 450 Cam
Stock Jetting
AP squirt: 1sec
Float: 8mm
Temps: 65-80F
Elevation: 800'
Air box lid removed
Air Screw: 2 turns

Performance Summary:
Starts and idles good. Good/smooth throttle response when cracking open from a stop.
Once I get past 1/2 throttle engine bogs down until I throttle back.

So far Ive tried a 170main and the stock 165 main. Needle clip is on #4 (middle). Im off to try the #5 clip position in an attempt to lean it but wanted to confer with the experienced on this before banging my head further.

  • clark4131

Posted December 15, 2005 - 05:05 PM


Going from #4 to #5 on the needle richens the mixture, provided you're counting from the top down. If you want to lean things, go to #3...SC

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  • 642MX

Posted December 15, 2005 - 05:50 PM


Your jetting actually sounds pretty close to me, almost sounds like something electrical?

  • NuckingFuts

Posted December 15, 2005 - 07:20 PM


Going from #4 to #5 on the needle richens the mixture, provided you're counting from the top down. If you want to lean things, go to #3...SC

Clark, my nomenclature follows that of the manual (sorry to confuse). Just so everyones on the same page from here on out I'll just say drop/raise needle for now.

I dropped the needle one position. Result: the bog is now at 3/8 throttle instead of 1/2 throttle.

So, I raised the needle one position (from my baseline #4) and the bog is now at 5/8 throttle. So Im moving in the right direction. But what's throwing me off is that with a 170 main and clip in #4 the bog still starts at 5/8.

I went back and re-checked my AP squirt and its more like 1.5 seconds (which is on the rich side). But Im not experiencing any bog off idle or when I snap it from 1/4 throttle. So, I dont think I'll play with that just yet. What Im thinking is that I may try out a YZ needle which is supposed to be more rich across the circuit.

Still bangin' away. :bonk:
I'll keep reporting back to the end so this thread doesnt become another open ended question that isnt much help for others in the future. 95% of these types of theads never get a final report from thread starter to say what solved the issue. :cry:

Thanks :applause:


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