Rich or Lean?

[Frank Castle]

Rich or Lean? which is better for 150cc scooters?

[Rhompin45]

A little rich, lean runs hot.

[Cubby1331]

I would run rich. If you run lean you have a chance of having detonation when you shouldn't have detonation. Remember Lean is mean

[Frank Castle]

which way is rich? clockwise (right) or counter clockwise (left) i have a carb with the mix screw on my left (choke side on cv carb) when sitting on my bike...this mixture screw thing is alittle confusing cause someone told me if the screw is on the outlet side (manifold side) its a fuel screw and if its on the inlet (air hose side) its a air screw, can someone confirm this?

[gitsum]

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.

[Frank Castle]

Originally Posted by gitsum

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