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mikuni TM 38. Does anyone no at what point the main jet comes into the circut half, 3/4, or full throttle?
 

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Im pretty sure the answer is 3/4, but lets see what the gurus have to say :lam:
 

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block catagorizing the metering circuits is not really representative of accual contribution. the main starts contributing as soon as the throttle opens. its major effects are seen above 1/2 throttle. all circuits, pilot, needle and main contribute all the time. but the % of effectiveness is different per throttle position.

bacially speaking the pilot is idle to 1/8th throttle, needle and needle jet are 1/8 to 3/4 and main jet is 1/2 to full open. this page http://www.lafishmag.com/CarbTuning.html will give you a pictoral idea. the Polaris manual has a very good section on tuning with very good descriptions and pictures. you can also look up Mikuni tuning on the web, lots out there. Brian.
 

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Quote: block catagorizing the metering circuits is not really representative of accual contribution

exactly. the fuel first flows thru MJ B4 it sees the NJ so a change in MJ may affect intermediate jetting(ever so slightly). now i think the idle is on its own circuitry with its own pilot(fuel) jet and air screw. VL series may be opposite on idle.
 
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