55 cub running badly

Mon Jun 30, 2014 11:50 am

Hey guys, I have a 55 farmall cub. Compression is fine and so is my ignition spark. Disassembled the carb to clean it and found the main jet broken in half. Bought one from an aftermarket place but it's only .030 and my manual calls for an .034. Put it in and it runs pretty badly. Idles ok but when applying the throttle it dies. Starts right back up. Should I drill this jet out or try to find the right size?

Re: 55 cub running badly

Mon Jun 30, 2014 12:43 pm

Welcome.

Main jet orifice diameter is not the problem.

Top of page "Trouble Shooting".

If you haven't done so, start with complete engine tune up; compression tests, valve tappets, ignition. Clean the air cleaner.

Re: 55 cub running badly

Mon Jun 30, 2014 1:41 pm

My Cub had always run rich. It finally got to the point it could not get out of its own way. Smaller jet courtesy of TM Tractor cured the problem. Carl says their are 4 jet combinations. Check out his carb how to.

Re: 55 cub running badly

Mon Jun 30, 2014 3:30 pm

I read in the international manual that if the top of the carb body is warped there is a chance it could suck air through the bowl gasket and upset the fuel air ratio. I discovered that mine is warped pretty bad. Is that why someone on here made a machined plate to straighten them? Can this cause a problem? If so, I will straighten it.

Re: 55 cub running badly

Mon Jun 30, 2014 5:16 pm

Yes and yes. There are folks on this site that repair carburetors. They have the jig for straightening tops and will go completely through the carburetor.