I've got a mikuni carb on my puma 196 mini bike, it has a stumble on hard acceleration, can anyone lead me to a good starting place to start dialing it in, air scre is at 2 turns out and the needle is in middle position, also have air filter and intake and a free flowing exhaust with a muffler. Thanks in advance
Mikuni tuning
- Thread starter cgersty
- Start date
Ian Williams Tuning has a great write up on Mik tuning. http://www.iwt.com.au/mikunicarb.htm
Your air bleed does nothing after idle. Since I am not there I can only surmise that you are running into lean conditions under acceleration.
Try moving the needle up from the middle position- (next lower detent) and that will slightly increase fuel flow under acceleration. Run it, and if it improves, go one more and see of that fixes it.
It "could" be that you are too rich, and if that was the case, you'd move the needle further down, into the main jet. But I don't think that is happening.
Your air bleed does nothing after idle. Since I am not there I can only surmise that you are running into lean conditions under acceleration.
Try moving the needle up from the middle position- (next lower detent) and that will slightly increase fuel flow under acceleration. Run it, and if it improves, go one more and see of that fixes it.
It "could" be that you are too rich, and if that was the case, you'd move the needle further down, into the main jet. But I don't think that is happening.
Could you provide as much information as possible on your setup? For instance what Mikuni carb is it? Is it the chinese one with a oval slide or the round slide one. What size is it. What are the current sizes of the pilot jet and the main jet. Does the spark plug look black or is it a light color. Pictures would help as well if you are not sure of the carb.
I'm pretty sure that this carb i have has a 26 mm air side but the carb to engine side is 22mm, matches up perfect to my buddies real deal 22mm mikuni, with that said, any idea for the starting needle clip position and the air screw is on the bottom rear of the carb? Sorry for the questions, just trying to get this running right for my kiddos to ride.
I answered your question in my post above. Post number two. You did fine starting with the clip centered, and once you leave idle (to 1/4 throttle), the air bleed and pilot jet is not in the equation.
Additionally, there is a nice thread here by carplayLB that does a side by side comparison of a "Chikuni" (Chinese Mikuni VM22) and an actual Mikuni VM22, and as I recall the venturi profile is indeed larger.
Additionally, there is a nice thread here by carplayLB that does a side by side comparison of a "Chikuni" (Chinese Mikuni VM22) and an actual Mikuni VM22, and as I recall the venturi profile is indeed larger.
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