Drilling out main jets?

Question

I have a 660 raptor, I need to drill out the main jets larger cause it is running lean, I have a drill index, does anybody know of a chart or procedure to drill them out so I use the correct size bit? for instance I want to drill out a 145 to a 165.

Answer 1

no drilling. u just need to install a larger jet. u'll ruin the carb if u drill it.

Answer 2

First, are you certain you need a larger main jet. MJ's control the fuel flow at about 3/4 or 7/8 throttle to full throttle. The needle in the slide controls the mixture from about 1/4 throttle to the point the main takes over. This is the area where the carb runs 90% or more of the time. Two or three very small washers, 1/8" placed on the needle to raise it will richen mid range nicely, likely all you need. If you think/know you really need to increase full throttle fuel, you should buy main jets, and do a full throttle, high gear plug check, or get a dyno run, to determine if more gas is needed. This should really be done first, then work on midrange. Doing main jets with no midrange correction will have almost no influence on mid range mixture.



If you do not understand the theory behind this, you may E-mail me with questions.



Tomcotexas



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Answer 3

A Hi-Performance won't drill'em out because it is just to simple to swap jets, drop the bowl remove main-jet and screw in the replacement (in your case..richer). In a few minutes your back down the road.

Answer 4

NO NO NO, you cant drill jets. jets are tapered to meet the needle and if you drill it will be a straight (not tapered) jet. needle will not match up. just buy some jets.

Answer 5

just buy another jet they are like 5 bucks and if you drill it wrong ur screwed