StarFire GT4 66cc


New Member
Jun 12, 2010
Hello. new to the forums here. I was looking at this engine kit that is sold at a shop up here in seattle. I was wondering what kind of tuning/performance parts i can add to it, to get it going 40+mph, and also make it so it wont blow up when i get it there. And dont worry i am not a newb.:D Thanks


a guy who makes cool bikes
Aug 18, 2009
living the dream in southern california
i've built three of these. i think they're awesome motors.

what i do is lap the heads down till the lip is almost gone, clean the transfer ports up in the case and the jug, get rid of all the casting flash in the intake and exhaust ports, match port the intake and exhaust manifolds, NGK BP7HS plug and 7mm copper-core wire, polish the inside of the carb, change out all the hardware to grade 8 allen head socket caps, adjust the flower nut on the clutch so it pulls with one finger, and i use Opti2 oil at 100:1 from the first tank on, and run it full throttle from the first fire-up. on mine, there's virtually no break-in period, and i run at 40+ all day.

one of my motors lasted at least 2000 miles, till the chain snapped and took out my rear motor mount and put a whole in the case. if it wasn't for that, it'd still be running.

put a new motor on the bike a few days ago, and rode 100 miles today at full throttle, going so fast, that if i posted my speed without proof, no one would believe me...

oh, and i also turn it around backwards.:)
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New Member
Sep 8, 2020
Hey y’all I’m Matthew! I just bought one of these Starfire GT4 66cc 2.75 hp and I was told the ratio for duke and oil is 2:1. To me that just sounds crazy so would you guys happen to know. Thanks. (Also I’m new to the forms)