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Posted

just installed some TM 38mm mikuni gas carbs on my 350 cub, I have 330 mains, 45 pilots, needle on the second clip from top, air screw 2 turns out....It Starts fine and everything but while at idle for a moment, it will start revving up by itself then will come way down...I've checked the slides, they are the same heights as well....why's it doing this?? Any help is appreciated

Posted (edited)

are your reeds in good shape with no gaps or small pin holes in them.

 

hopefully you dont have a small air leak you might spray some starting fiuld around your intake. a small amt. do get carried away. or boom starting fiuld is flammable as hell.

Edited by wesw
Posted

I'm starting to wonder if my pilots are too big because I have fuel running out of my overflow on bottom of bowl too....I bought the carbs new and they came with a 22.5 pilot....I put in a 45 just because I'm going off of similarity of Mikuni 34's....not for sure though, very possibly could be an air leak in my intakes too...

Posted

does it start with out the chock, if so then you have a large pilot and need to go down.

 

i ran a 68 pilot on my pj34 it was huge but still idled. but it would load up like a bitch so i changed it down.

Posted

i have noticed mine does about the same thing, not too bad, but it does go up and down. i think it always has, and i have done tons of carb removals and installs and even rebuilt the top end, i thought they just did that????

Posted

generally a motor will rev up like that when starving for gas. do you have to choke when you start it? after its been idling for a while when you rev it up does it sound sluggish and blow some smoke out or does it rev out clean? i wish i knew more aout those carbs but from the revving up and down i would guess either an air leak which would cause you to lean out, or your pilot is too lean...let it idle for a little bit and then oull your plugs out. see if they are really wet or kinda dry...

Posted

when I let it idle and rev it up it puts out a lot of smoke, my plugs are also dripping wet, so I know I'm not lean.....I also DO NOT have to choke it with the 22.5 pilots I put back in it...so I'm not for sure if this is normal or not....I wouldn't think so because it didn't do it with the 34's on it

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