Help on fuel/carb issue

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feg7846
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Tractors Owned: 1947 Cub
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1986 Kubota 38
Location: Gordon, Georgia

Help on fuel/carb issue

Postby feg7846 » Sat Nov 28, 2020 6:15 pm

I am working on a 1947 cub for a friend. It has been sitting up for about 6 years. When I got it, I converted it to a 12 volt ignition system, rewired the whole electrical system. Got a great spark to all cylinders. Moved on to carburetor and rebuilt it. Been working on it for about a month as time permitted. Went to try and start it today and it would not run. Motor turns over very well but no start. Only have carb on tractor at this point, do not have the air filter system hooked up yet. Thought I would try and get it running before I did the air filter. When trying to crank it, it would sometimes backfire out the air inlet on the carb and when I stopped trying to crank it, a few drops of fuel wold also come out of the air inlet end of the carb.Tried some starting fluid one time, nothing there either. Any ideas or suggestions. I am pretty much at a loss right now. :help:

Jim Becker
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Re: Help on fuel/carb issue

Postby Jim Becker » Sat Nov 28, 2020 6:32 pm

First, prime the oil pump if you have not done so. Then redo the timing.

Eugene
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Re: Help on fuel/carb issue

Postby Eugene » Sat Nov 28, 2020 6:57 pm

Jim Becker wrote:First, prime the oil pump if you have not done so. Then redo the timing.
And then compression tests, looking for valve(s) stuck open.
I have an excuse. CRS.

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Dale Finch
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Re: Help on fuel/carb issue

Postby Dale Finch » Sat Nov 28, 2020 8:04 pm

And double check that the spark plug wires are going to the right plugs...the order (clockwise looking forward) from upper right distributor tower is 1-3-4-2, and plugs from front to back, 1-2-3-4.
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feg7846
5+ Years
5+ Years
Posts: 87
Joined: Mon Jul 02, 2012 7:05 pm
Zip Code: 31031
Tractors Owned: 1947 Cub
1969 Cub
1986 Kubota 38
Location: Gordon, Georgia

Re: Help on fuel/carb issue

Postby feg7846 » Sat Nov 28, 2020 9:14 pm

Yep, had read in another post about priming oil pump, so I did this before trying to crank it.
Will redo timing tomorrow and see how that works.
Took the side cover off right before dark to look at valves, but will take a look at them tomorrow.
Pretty sure plug wires are in order, but will also recheck that tomorrow.

Thank you my friends. Any more advice, keep it coming.....

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Glen
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Re: Help on fuel/carb issue

Postby Glen » Sat Nov 28, 2020 11:14 pm

Hi,
They have said on here that it is normal for the Cub's updraft carburetor to leak a little gas out the air intake, or the drip hole on the bottom of the air intake, if you crank the engine over, and it doesn't run.
The gas is sucked up towards the engine, but runs back down, because the engine didn't run.

You didn't say if the Cub has a magneto, or a Battery Ignition unit. :)

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MiCarl
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Re: Help on fuel/carb issue

Postby MiCarl » Sun Nov 29, 2020 7:33 am

Not lighting starting fluid is a sign of ignition (no spark, timing, plug wires to wrong place, bad plugs) or very poor compression.

I'd go back through the ignition system making sure it's timed properly and the wires go to the proper plugs. Once I was sure that's right I'd put in new spark plugs. A fuel fouled spark plug will often fire outside the engine but be useless in the cylinder.
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1948 Farmall Cub
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