18mm cv pumper carb

GoldenMotor.com

captainrichhill

New Member
May 31, 2008
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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.
 

john_the_great

New Member
Oct 24, 2009
191
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California
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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john_the_great

New Member
Oct 24, 2009
191
0
0
California
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.
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.
 

mountain80

Member
Aug 8, 2008
260
4
18
Red Deer, Alberta
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.
 

john_the_great

New Member
Oct 24, 2009
191
0
0
California
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.
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.