Super A surging after carb swap

Hi, I searched through the forums and found a lot of useful information on how to adjust the governor and set the float level on the carb, I tried them all before posting and got nowhere. I also went through the I&T manual.

I replaced my carter carb on my 48 Super A with the Zenith one from this website. When the tractor would actually start and run with the carter carb it ran decent but too rich. I had a hard time finding a rebuild kit for it so I finally went with the Zenith.

The first thing I noticed when adjusting the governor linkage was that I had to shorten the linkage within a turn of the shortest I could make it. When I got the tractor to start it surged and low idle seemed to be at 1/3 throttle. When I took the acorn nut off to adjust the governor it was pretty much adjusted in as far as it could go, backing it out did nothing to help.

So, since it didn"t do this with the carter carb I am wondering if something with the zenith carb is causing it. Also, the only adjustment screw on the zenith doesn"t seem to do anything. I am hoping it is something simple with the carb since that looks easier to mess with than the governor.

Thanks for the help.

There should be 2 adjustment screws, one for idle speed, one for idle mixture. There is no main mixture adjustment on the gas carbs. About all you can do is adjust the float level. There are several Zenith carbs that will bolt on. You need to determine which one you have by looking at the parts manual, I believe that there are only two Zenith gas only carbs that IH sold for the Super A, although other models should work. Could be that someone messed up the carb and returned it. Since this site does not repair carbs, they could have resold it. This is only a possibility, not an accusation. It sounds more to me like you have a governor problem.

It also would be good to make sure there are no leaks at the intake ports on the head/manifold gasket. If there are it could be sucking raw air and the carb not getting the full strength vaccum.

As far as I can tell you're right, the adjustment screw on a zenith doesn't do much of anything. I replaced the carb on my 49 super a and the new carb acted just like the old one. My tractor sat in a barn for 3 years and was converted to a battery ignition. i wanted to go back to the origional so I rebuilt the Mag and got it started. It ran rough and popped back through the carb. The popping was two spark plugs switched. I fixed that but it still missed. All the adjusting in the world didn't make any difference.I set and reset the points, regapped the plugs. nothing. still missed and was hunting. I pulled the governor housing off and found the spring had jumped off because the idle arm was upside down. repaired that and adjusted the governor until the hunting went away. Still missed. The only thing I knew i had done was to gap the plugs at .025 so I pulled them out and reopened the gap back to what they looked like out of the box. Now it runs perfectly but the governor does nothing. I have a hard time believing that the plugs had that much impact on how it runs. I know the governor has a lot to do with how it runs so I don't think you have a carb problem. Did you try adjusting the governor and carb linkage by the IT manual. Before you do back the governor adjustment screws out and then try adjusting them in. post your results please. So many folks when the find the solution don't post it so we out here don't know what works.

I have a used governor on order that is supposed to be in good working order. Once that comes in I will let you know how I make out.

I did adjust the linkage by the I&T manual, I pretty much had to adjust the yoke all the way down on the rod so that is making me think that something is worn out or not right with the governer.

As always, thanks for the help and suggestions.