Motorized Bicycle General DiscussionTopics on bicycle engine kits, help articles, repair and modifications for your motorized bicycles
how to redrill main jet?
Discussion at Motorized Bicycle Engine Kit Forum in the Motorized Bicycle General Discussion forum. can anyone tell me how to redrill a main jet properly?...
find a hardware store that sells jewlers drill bits, take your jet in with you & find the # bit that fits your jet. (probably a #70 bit) Then use the next size bigger to drill the jet. DON'T DRILL IT TOO BIG!!!
After you drill it one size bigger & put it back in the carb and take the bike for a ride.
If it seems to run a little better but not yet perfect then drill it again with the next size up until it runs good. AGAIN!!! DON'T DRILL IT TOO BIG!!!
If it runs worse, then you know you need to make the hole smaller.
Also after drilling you might want to experiment with the needle positions, this also makes a difference from idle to mid throttle, then the main jet takes over......
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you make the hole smaller by filling it with solder, right?
Yep!!
Make sure you remove all the extra solder from both ends of the jet!!
(Make sure you don't go too small... running too lean is a very bad thing!)
I may have drilled my main jet too big. The engine lacks accelleration, has a slower top speed and has a slow idle. are these symptoms of a rich mixture?
I would try moving the needle clip UP a notch and trying it. It will make it leaner, idle thru mid range....
What size was it before you drilled it? What size did you drill it out to?
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"No such thing as a stupid question, just a stupid answer"
48cc Grubee Starfire Round Head......
Last edited by misteright1_99 : 07-18-2008 at 11:08 PM.
how to redrill main jet? 
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