I have a 1980 Puch sport MKII and I have a proma circuit exhaust coming along with a 15mm bing carb and a 15mm intake plus high flow filter. My question is will i need to upjet? or should that carb be fine? the motor is otherwise all stock. Oh and i do have a 20 tooth front sprocket on it if that makes any difference.
If I'm remembering correctly, the 15 Bings come with an 82 (?) jet. That's probably a little high for your setup -- I run a 78 with a similar setup, and that's higher than what most people run. Basically, whether you need to upjet or not will be determined by the jet size that comes in your carb. If it's too big, you need to downjet, and if it's too small, you need to upjet.
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