1949 Cub Fuel System(?) Troubles

[ParlowMillFarm]

I had the same symptoms as the 1948 Cub in an earlier string. But its not the same cause (although my cause is not yet determined).

The cub starts right up and runs fine for a minute then sputters then stops. Sounds like its running out of gas. This is a IH carb.

I tried the following;
New gas
clean sediment bowl
disconnect fuel line at carb and check gas flow
clean screen in carb, with carb cleaner and a blast of air. (check flow with water when washing off carb cleaner.)
Check needle valve and all interior tubes and vent holes. ream out with wire and air blast
Remove idle jet and wire out then air blast. set idle jet at 3/4 turn
clean main jet with wire and air blast
check flow to bowl by removing plug
new plugs
retime

One odd thing. The upperpart of the carb sweated (got condensation on it) when running

All above produce no change in Cub behavior. Suggestions?

[Jim Becker]

Check for spark at the spark plugs. If it is much worse after it stalls than before you start it, you have an ignition problem.

[Eugene]

How long after tractor dies will it start up? If wait is 10 to 20 minutes, ignition problem. 2 or 3 minute wait, fuel.

[Don McCombs]

Set "idle jet" at 1-1/2 turns out, not 3/4.
With a flashlight, inspect the interior of the fuel tank at the outlet, looking for debris. If you have debris or rust, remove it.

[ParlowMillFarm]

Well I have three Masters replying so I am out of the dumps thinking this won't be fixed.

Jim, I have a traveling mechanic who has something to check strength of spark, I'll check it out.

Eugene, After it die I can start it right up but it only runs for a few seconds.

Don, I will reset the idle jet to 1 1/2 turns. ( I think that's what I had it at to start, but one of the manuals said factory setting was 3/4....) There was a little rust to start in the sediment bowl. That was cleaned out and I have a strong flow to the carb.

I will report back after I try the Idle jet adjustment.

Thanks for replying!

[SamsFarm]

Don, There was a little rust to start in the sediment bowl. That was cleaned out and I have a strong flow to the carb.

I think what Don is implying is that you remove the gas cap, take a flashlight and shine down onto the tank on the hole you see where the fuel bowl is screwed to the tank!

Look for someything there!

If he is not implying that, then I suggest you do it!

If you have strong fuel flow to the carb, do you have strong flow out of the carb?

There is a pipe plug in the bottom of the fuel bowl, you can remove and let the fuel flow into a container.

Let it flow longer than the time it takes for your running problem to show it's nasty face!

[Don McCombs]

I think what Don is implying is that you remove the gas cap, take a flashlight and shine down onto the tank on the hole you see where the fuel bowl is screwed to the tank!

Look for someything there!

Sam is correct.

[elongest]

Not trying to hijack this thread but. I have 51 (new to me) with just about the same issue. With the orig. installed zenith carb it will start and run with choke 20 sec to 1 minute. Did all the above-mentioned steps and have good fuel flow out of the bottom of the bottom of the carb bowl. Tried two China carbs, starts on choke only and runs with choke only about 20 sec. The tractor runs good when running then shuts off. After a few seconds it will restart and do the same thing. IT shuts off when ever you turn the choke off. The engine was suppose to have been rebuilt before it sat for a couple of years. I'm leaning towards a vacuum issue, maybe a stuck intake valve. I see a plug in the intake manifold I might could tap into or might as well check the compression first. Any other suggestions.
Eddie

[Bob McCarty]

If you haven't opened either Chinese carb, it's likely the float is not set correctly and there have been some that don't have a hole drilled into the air intake. (couldn't find Don McComb's post with the photo)

[Don McCombs]

[elongest]

Just a follow up on the 51 Cub. Drilled hole and adjusted the float in the new Carb, it starts up and runs with no choke now.
Thanks for the info.
Eddie

[Don McCombs]

For those that need to complete the drilled hole, the hole size is not super critical. The hole in the original IH carb is 11/64. You can't go wrong with that bit. Make sure you don't drill too far and damage the choke plate and/or the choke shaft.

[fireman72737]

Just a follow up on the 51 Cub. Drilled hole and adjusted the float in the new Carb, it starts up and runs with no choke now.
Thanks for the info.
Eddie

How did you adjust this type of float? I have the same carburetor with very similar issues. The hole in mine was t drilled so I did and it didn’t seem to change much. It will run a few seconds then die.

[Bob McCarty]

The float is adjusted the same as if it was brass, just harder to bend.