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Turbocharged, Supercharged, and Hotrod Motorcycles: [turbobike] needles

[turbobike] needles

mos topher (mostopher@hotmail.com)
Tue, 18 Aug 1998 14:20:39 PDT

Does the bike with the huge dip in the dyno chart have CV carbs or 
Racing carbs??  
Racing Carburetors don't really care what RPM you are at, all they see 
is engine vacuum. To figure out which carb component has the most effect 
when trying to cure a jetting problem you should take note of throttle 
position.  Each component is related to a specific throttle position, 
not RPM. The following is a basic chart that shows which jet has the 
most effect on a certain throttle opening.

Idle - 1/4 open     Slow Jet/Fuel Screw

1/8 - 3/8 open     Jet Needle Diameter & Needle jet

3/8 - 5/8 open     Jet Needle Clip Position

3/8 - 3/4 open     Jet Needle Profile (taper)

3/4 - 4/4 open     Main jet / Main Air jet

This is true for most mechanically operated carburetors, CV carbs are 
different as the slide is directly controlled by engine vacuum instead 
of your wrist.


>> First I don't think that could be needle taper because generally
 >>needle taper affects 3000 to 5000 rpm, needle height affects 5000 
>>to 7000 and the main jet affects 7000 on, that's from my jet kit
>>instructions.

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