jetting/carb debug help (cont.)

Ernest Montague afm199 at
Sat Aug 28 07:51:53 PDT 2010

You are lean for that setup.  6k is probably mains. If that is the big 
mouth BMC that is open all the way across, you are very lean.   If it 
is the standard BMC race filter you are still lean. BMC made two, one 
for factory pro that was wide open, one with an opening like the stock 
filter.  Either way you are very lean.

Stock race BMC try 150-160, Factory Pro BMC try 160-172,  open fuel 
screws 2.5,

If the needles were a problem it would start much lower.

On Aug 28, 2010, at 2:55 AM, matthew patton wrote:

> I'm working off the Factory Pro v1 kit and a BMC race filter + yosh 
> race pipe. Per their instruction sheet:
> 140/142 mains
> Factory needle at 3 clips
> 2.25 turns on mixture
> 0-6000 RPM works pretty much flawlessly.
> from 6000 rpm at any throttle opening of 1/16 or more the motor bucks 
> and gags and refuses to run.
> Is my needle circuit working at all? I'm guessing that the slide isn't 
> rising near fast enough when the butterfly opens.
> I've pushed on the slide and they return home from full up in about 
> "one thou" (speak 'one thousand').
> If the slide is too slow to rise, what do I need to fix? Would any of 
> the little air jets in the mouth of the carb be the problem?
> Or is it all 'mains' from 6000+ on up?

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