Need Jetting Help

99blaster:)

New Member
Aug 18, 2010
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Upstate New York
im finishing the rebuild of my blaster and need some jetting sizes. it has an fmf fatty pipe with shorty silencer, uni foam filter with holes in the airbox lid, mild trail port and polish, bored .040 over with a wiseco prolite piston, boysen pro stock reeds, +4 mil stroker crank, running on 93 with klotz octane booster, and thats about it for the motor. any help would be greatly appreciated because im gonna have to order some jets tonite if i want to have it back up and running for this weekend!I:I
 
I presume it is a stock carby.

A range of main jets from #280 to #320, stock pilot, needle on middle clip.

I guess its cold there so start big, and do plug chops for each jet.

You should consider a larger carb , it would make a lot of difference.

Whats with the octane booster, can you not get a fuel with a higher octane rating?
 
just something to think about... you would probably get better performance running a lower grade octane. Im not sure your compression but I don't think you have anything too wild. High grade on a stock or mildly modified motor is actually counter-productive sometime. Something to think about. I used to be the "run premium or better in everything" guy but then I did a lot of research and found out that I not only got better performance from lower grade, but I also got better mileage as well. The rule of thumb is you want to run the lowest grade possible without detonation.

this might help you on the jetting. And also, when you jet, start with your pilot circuit first, then move up from there. Get it running, warmed up and set your idle a little high... then play with your air screw until you get the fastest idle possible and leave it there. Then shut it down and count your turns out on the airscrew. If it isless than one turn out, go bigger on your pilot, if it is more than 2-2.5 turns out, go smaller on your pilot. (or maybe its the other way around - someone wanna chime in>) then go from there.

- Justin
 
on the stock 26mm Mik, there seldom is a need to change the pilot, the carb simply doesnt flow enough air to warrant a bigger pilot, you can almost always tune with the 32.5. Although i tried a 35 once, i found the 32.5 still worked best with my mods. im sure others will agree
 
thanks for the help and before the motor was only .020 over it had everything else on it but its got a high compression piston now and its tough to get good gas around here thanks for the help :)