18mm cv pumper carb

john_the_great

john_the_great

New Member
This carb I found goes to the 50cc 4-stroke gy6 139qmb scooter motors put on modern chinese scooters. What is remarkable about this carb is it is a tiny PUMPER carb! It also a CV carb! I am seriously considering ordering one.

50CC MOPED CARBURETOR CARB KAZUMA SUNL ROKETA BIKE CA13

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I considered one of these too. However, I was unsure if it being a carb for a 4 stroker would make it tough to tune. I thought I read on this forum somewhere that could be a problem.
Does anyone know how different it is being a 4 stroker carb vs. a 2 stroker carb. Does a 4 stroker have larger jets since it's delivering the fuel/air charge only halve as many times per revolution of the crank? I'm not sure.
 
The reason I like this carb, is its the smallest carb I have ever seen with an accelerator pump and a cv. It has the same technolgoy in it that modern dirt bikes/street bikes have. It is way more "high performance" then the equal size mikuni. The smallest accelerator pump carb they make is 28mm and it isn't cv.
 
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captainrichhill said:
I considered one of these too. However, I was unsure if it being a carb for a 4 stroker would make it tough to tune. I thought I read on this forum somewhere that could be a problem.
Does anyone know how different it is being a 4 stroker carb vs. a 2 stroker carb. Does a 4 stroker have larger jets since it's delivering the fuel/air charge only halve as many times per revolution of the crank? I'm not sure.
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Actually, on average 2 strokes have bigger jets because it pulls more fuel and air. Also I have never seen a cv carb used on a 2 stroke so this would probably work best as a high performance upgrade for a 4 stroke motor.
 
My question after tuning 4 stroke cv's for years on motorcycles is can you buy different needles for it?? There is no 1 needle fits all for the world just doesn't work that way. Also tuning cv carbs is a diiferent ball game as you have to start drilling the orifice that bleeds air to the diaphragm to change the rate the slide opens as it is not controlled directly/mechanically. If their tuneable with different needles go for it. Also one of the differences between 2 and 2 strokes is the diffuser nozzle- the brass tube that the main jet sits in. 4 strokes usualkly have more holes to allow air/fuel mixing to occur while 2 strokes have less as they prefer a richer mixture.
 
mountain80 said:
My question after tuning 4 stroke cv's for years on motorcycles is can you buy different needles for it?? There is no 1 needle fits all for the world just doesn't work that way. Also tuning cv carbs is a diiferent ball game as you have to start drilling the orifice that bleeds air to the diaphragm to change the rate the slide opens as it is not controlled directly/mechanically. If their tuneable with different needles go for it. Also one of the differences between 2 and 2 strokes is the diffuser nozzle- the brass tube that the main jet sits in. 4 strokes usualkly have more holes to allow air/fuel mixing to occur while 2 strokes have less as they prefer a richer mixture.
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I haven't found needles for this carb (and never have had to buy any for a cv before) that is a flaw with this carburetor type, although I have found jets for it. ....so maybe its not adaptable enough. I think though since it came off a 50cc motor it might work on the bicycle 50cc 4 stroke.
 
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