Mikuni carb pilot and main jet adjustment

CJdoodlebug90

CJdoodlebug90

Member
#1
#1
Ok so i have a mild built 212cc. Installed a 26mm mikuni with 130 main jet and 12.5 pilot. Ive kind of been going in circles with trying to tune it. What is a good needle setting and mixture screw setting to start with? Ive got it to run decent but it boggs after free rev and sonetimes backfires when pull start.
 
ole4

ole4

#2
#2
130 works on all of mine and clip in the middle. Pilot varies from 12.5, 15 or 17.5. You should be able to adjust the idle air control needle to get a good idle between a 1/2 turn to two turns out if not see where it idles best below 1/2 turn you need a bigger pilot jet, if over two turns out you need a smaller one. When you adjust the idle air screw if it starts to idle too fast open up the slide height adjuster to lower the slide then repeat air screw adjustment once idle is best turn in idle air screw from a quarter to a half turn in to richen it up a bit and prevent stalling on releasing the throttle. Takes a bit of practice but you will get better with practice. Now I am assuming your valves are set correctly and no air leaks in intake system. This is a CHI MIKUNI with the oval slide hole when you look thru the carb correct?
 
delray

delray

Well-Known Member
#6
#6
i may be wrong on this? but wouldn't you want to start out with a 22mm carb? or is there alot of performance up grades you have done on the engine. for example. head ported big valves...cam...etc..
 
ole4

ole4

#7
#7
They really are about 22mm just the outlet is 26mm. I have them on 5 hp tecs and they work great. The oval slide opening acts like a small carb at small throttle openings and also gives more granularity so it is not like a on off switch.
 
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