Thread: Rich or Lean?
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Old 04-22-2014, 10:18 PM   #6
Frank Castle   Frank Castle is offline
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Join Date: Feb 2014
Location: MIAMI
Posts: 196
Quote:
Originally Posted by gitsum View Post
If the air/fuel screw is closer to the engine manifold side of the carb, it is a fuel screw. Righty tightly, lefty loosely. Tighter is less fuel, looser is more.

If the air/fuel screw is on the airbox/intake side of the carb, then it is an air screw. You are then adjusting the amount of air in the fuel ratio, tightening is less air making things richer.

That being said most GY6 scooters have a CV carb with a fuel screw.

The fuel screw will have the biggest effect on the low range (up to 1/4 throttle) and a smaller effect on the midrange or needle jet. It won't make much difference for the main jet. If the carb was originally tuned very lean to pass emissions, it is sometimes necessary to raise the needle jet and install a larger main jet to get things running optimally, just a fuel screw adjustment isn't enough. This is especially true if opening up the air intake and exhaust.
ok so now i know i have a fuel screw, and i unscrewd it so it can be on the rich side, as far as jets, i upgraded my main jet to 108 my new carb came with a 105
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