Air / Vacuum leak, stock carb??


New member
I am looking for what I think has to be a vacuum leak - hard starting and choke has no impact on running engine. Governor removed, ARC flywheel, performance air filter and exhaust, E tube and .036 jet. Once started after 15 pulls, idles and runs but closing choke has no effect on idle. The only changes this time are carb E tube and jet and flywheel. 32 degree advance wheel but using 4 degree timing key backwards to retard to 28 degrees since stock cam.
The only thing I see is the air passages on the head side of the carb - passages to outside air in both carb gasket surface and plastic spacer.Those passages are open to approx 1/8" ID hole/passage in carb base so outside air can feed to the passage in carb. This is all factory stock carb except E tube and jet. Are those passage to remain as is? I see nothing about blocking in any info on carb mods.


Dawg 89
it vents the float bowel through the back of the carb . I suspect that's what you're looking at.
you have the air filter adapter on correctly ? it can be upside down covering the air bleed holes.
otherwise spray an aerosol lubricant around the carb it will show a leak.


New member
Thank flattop1, I figured that out. I used spray HighTack on gaskets and put it back together. The only thing I found was that the plastic choke lever was hitting the rubber collar on the air filter, not allowing it to completely move to the closed position. It wouldn't have held the flap open much at all but maybe just enough at idle to not function properly.


If you spray around the carb with WD40 and find no leaks, I would dismantle carb again something is installed incorrectly, these engines should not take 15 pulls to start. Cany ou see the top of the Emulsion tube projecting into the venturi? Is the jet tight in place? Do you or have you checked the o rings on the pilot jet, has the idle air screw fallen out?


New member
Thanks all. I found two things but no air leak. Choke lever was not moving to "choke" position completely, it was hitting the rubber shoulder of the air filter. Probably more importantly, I found that without governor, it wants a little throttle to start. Starts right away now. All gaskets and e tube were correct.