IH Carb Problems

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Plywud
Posts: 48
Joined: Sun Aug 23, 2020 6:45 pm
Zip Code: 98042

IH Carb Problems

Postby Plywud » Thu May 06, 2021 6:32 pm

I rebuilt my 1948 Cub IH carb about 6 months ago and it's been working fine up to now. Problem is flooding after attempted start or after started and turned off. Fuel is leaking out of a fixed plug insert, on the choak end of the carb, underneath the choak tunnel for lack of a better term. This is not the brass screw in plug farther back on the same casting. Took it apart again, float is working, can blow air through fuel inlet fine, can close the float and the air is cut off completely. The little brass lever under the float tab moves mostly freely when I move the float up and down, sometimes it sticks in the up position for a few seconds. I can let the carb drain and dry out over time, so it's not leaking from the plug, turn the gas value back open on the sediment bowl and the carb will not leak until I try to start it. Have not changed any of the adjustment screws since the original overhaul.

Anybody got a clue here what I'm doing wrong?

Thanks

RJ

Bob McCarty
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Re: IH Carb Problems

Postby Bob McCarty » Thu May 06, 2021 8:36 pm

Check to make sure the choke lever isn't slipping on the shaft. Take off the air intake hose and watch the butterfly as you move the choke lever. Did you check the float for leaks? Immerse in hot water and look for a stream of bubbles.
"We don't need to think more,
we need to think differently."
-Albert Einstein

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MiCarl
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Tractors Owned: 1944 Farmall H
1948 Farmall Cub
1994 Speedex 1631
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Location: Livonia, MI

Re: IH Carb Problems

Postby MiCarl » Thu May 06, 2021 9:03 pm

Updraft carburetors have that drain where you're dripping fuel to drain off fuel that condenses in the intake manifold. While it will also leak there if you have a float problem it's not unusual for fuel to drip on any fail to start condition, particularly if you're using the choke.

Since it's not leaking until you crank the engine I suspect the problem isn't with the float or needle. Check the choke as Bob says then start looking for non fuel system problems (spark plugs, ignition system, timing, compression etc.).
1944 Farmall H
1948 Farmall Cub
1994 Speedex 1631

Plywud
Posts: 48
Joined: Sun Aug 23, 2020 6:45 pm
Zip Code: 98042

Re: IH Carb Problems

Postby Plywud » Fri May 07, 2021 4:02 am

Will check the float for leaks. Just had the mag rebuilt professionally, did the line of the mark on the crankcase after the first click, set the rotor to top and installed. Move mag up against the block, crank engine around again waiting for two clicks this time. Mark was off about 2 inches. Moved the mark back to line up with the pointer then back to the mag. to move it away from the block, was suppose to click but mine didn't. Set up everything else and tried to start but failed. Gave up and just moved to TDC, pointed the rotor to just before number 1, reset and it started right up. Ran a little rough and then died. Fuel leaking out of the carb, failed to restart. Spark plugs are new, compression is 90 - 100 - 95 - 100. I did find where the choke lever had moved on the connecting rod, pushed in full was full choke, pulled out was full open. I fixed that and reinstalled, failed to start. Carb has never leaked before in the various testing and runs to check problems fixed, I know because I park it in the garage, and I watch the floor for oil and hyd leaks. Does any of this help analize?

RJ

Gary Dotson
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Re: IH Carb Problems

Postby Gary Dotson » Fri May 07, 2021 7:31 am

The rotor, in the mag, must be timed according to the timing marks. If you moved the rotor off that setting, you just tried to put a band aid on the real problem. I believe your governor is 1 tooth out of time. Re-align your rotor timing marks and repeat the process, if it still snap when rolled away from the engine block, re-time your governor.

Plywud
Posts: 48
Joined: Sun Aug 23, 2020 6:45 pm
Zip Code: 98042

Re: IH Carb Problems

Postby Plywud » Fri May 07, 2021 9:44 am

Thank you guys, never a dull moment with this hobby

RJ

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Glen
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Re: IH Carb Problems

Postby Glen » Sat May 08, 2021 1:50 am

Hi,
Below is a pic of how the magneto drive should be turned when the engine is at number 1 cylinder TDC. :)
Attachments
Cub gov gear.jpg

Gary Dotson
Team Cub Mentor
Team Cub Mentor
Posts: 4908
Joined: Thu Aug 03, 2006 6:20 am
Zip Code: 43358
Tractors Owned: 48 Cub Diesel (Cubota)
53 Cockshutt 20 restored (Shooter)
52 Cockshutt 20 unrestored
47 Leader "B" (Herckie)
49 Leader "D" (Princess)
49 Leader "D" very rough
48 Leader "D" unrestored
Kubota B6200E
Kubota B6200HST
Kubota B8200HST-D
Circle of Safety: Y
Location: OH West Mansfield

Re: IH Carb Problems

Postby Gary Dotson » Sat May 08, 2021 7:05 am

I meant to say: still will not snap when rolled away from the engine block, sorry bout that!


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