Carb problems

Sat May 11, 2013 3:04 am

I'm going over a 1950 Cub recently purchased and have a carb problem. It was flooding out and getting rust in it, so I had a mechanic (who was the IH dealer here) clean and seal Kote the fuel tank. I asked him to put a kit in the carb but he said it only needed cleaning which he did.
So I put it all back together and had two problems.
One- one of the two bolts that mount the carb had stripped the threads and can't be tightened properly. Its too close to put a nut on the bolt so what is the fix for this? Drill out and rethread one size up?
Two- the carb seemed to flood and drip fuel from the bottom just like it did before, and the tractor would not crank.
I know where i can get a used engine with a carb on it for probably $150 which might be good to have on hand.
any suggestions? I need to cultivate my corn patch, the weeds are growing !

Re: Carb problems

Sat May 11, 2013 5:13 am

The stud can be drilled out and a helicoil inserted and keep it the same size which is the proper way to fix the stud, or you can get a small nut and grind the shoulders down and with patience get it to fit. Do not cut out the carb so the nut will fit, it damages the carb.
Sounds like the float is still out of adjustment to let the carb drip, or there is still trash in the system or a speck of something in the needle and set. I assume the settlement bowl was cleaned out and a new screen put in, if not it should be.
150 bucks for a motor if it is not a rust bin or frozen up, yea, I would by it. Carbs can usually be fixed with a little tinkering and adjustment.

Re: Carb problems

Sat May 11, 2013 6:00 am

It is an updraft carb, so if your engine is not starting fuel is going to run back down to the lowest point. Completely normal.
The carb is probably the last place to look if your engine is not starting, but here is a quick check I use: Spray a little carb cleaner in the carb intake while the engine is cranking. If it fires with carb cleaner, you have a fuel delivery problem. The first thing I would do is pull the brass nut on the side and clean the jet with a soft copper wire and compressed air. If you have junk in the fuel system, this is where it gets clogged. If you ever find you need to suddenly run on choke and lose power, go straight to the jet and clean it. Many carbs are needlessly rebuilt and if the wrong kit is used you will end up worse off than before.

You can see the nut here thanks to TM Tractor's photo archive:


Re: Carb problems

Sat May 11, 2013 6:19 am

Stripped threads on the carb flange are quite common. The best repair is to helicoil them, but an acceptable solution is to grind the side off of a nut so it will fit in there. Please don't start drilling stuff oversize. I'm with Bob, I think you need to check out the basics, to get to your no-start issue.

Re: Carb problems

Sat May 11, 2013 8:01 am

Auto parts or hardware store probably has studs with two different thread diameters. 1/4" on one end and 5/16" on the other. The process is to drill and tap the striped out threads for 5/16".

Re: Carb problems

Sat May 11, 2013 9:21 am

There may have still been some rust in the sediment bowl or fuel lines that did not get flushed out, ad you may need to just clean the carb again.

Re: Carb problems

Sat May 11, 2013 11:18 am

Thanks for the info. I will let you know how it goes.

Re: Carb problems

Tue May 14, 2013 5:59 am

Well I got her fixed. But not without difficulty.
The helicoil tang broke off before it was fully seated, so I had to drill it out. I managed to grind off the side of a nut and get that on.
Thanks for your help!