cub wont start

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brianc1471
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Joined: Mon Mar 09, 2015 8:40 am
Zip Code: 27344

cub wont start

Postby brianc1471 » Mon Mar 09, 2015 8:47 am

I recently purchased a 1949 cub. It was running great but had a radiator leak and a small carb leak. I changed the radiator, put new gaskets on the carb, put new plugs and wires, changed the oil and filter, and now it will not start. The carb leaks worse now than before. I'm sending it to be rebuilt but want to make sure I'm not missing something. I can't get the tractor to start with starting fluid either. It backfires and that's it. Any advice will be greatly appreciated.

Eugene
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Re: cub wont start

Postby Eugene » Mon Mar 09, 2015 9:28 am

Spark plug wires on wrong spark plugs.
I have an excuse. CRS.

Bob McCarty
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Re: cub wont start

Postby Bob McCarty » Mon Mar 09, 2015 9:31 am

Brian, Welcome to the Forum. Check to make sure you have your plug wires in the correct order (1342). Backfiring means the timing is off. If the carb leaks when you're choking it and the engine doesn't start that is probably normal. If it leaks continuously then you have a problem with the needle valve and seat or the float. The new wires also need to be solid ccopper core and not graphite.

Bob
"We don't need to think more,
we need to think differently."
-Albert Einstein

brianc1471
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Joined: Mon Mar 09, 2015 8:40 am
Zip Code: 27344

Re: cub wont start

Postby brianc1471 » Mon Mar 09, 2015 10:23 am

Thanks for the responses. I've got plugs as 1 on top right, 2 on top left, 3 on bottom right, and 4 on bottom left. Plugs are 1,2,3,4 starting from the front, right? The diagram in the manual is kind of hard for me to tell, but I think that should be right. I'll check the wires to make sure I have the right kind. I'm sure it's something simple but this is my first old project tractor.

Bob McCarty
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Re: cub wont start

Postby Bob McCarty » Mon Mar 09, 2015 10:45 am

The wires go in order around the distributor cap, but not in order on the spark plugs. #1 plug wire on cap goes to spark plug closest to radiator. #2 plug wire on cap goes to #3 spark plug. #3 plug wire on cap goes to #4 spark plug (closest to driver), and #4 plug wire goes to #2 spark plug. That's how you get the 1342 order that is on the head.

Bob
"We don't need to think more,
we need to think differently."
-Albert Einstein

rjohnson
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Re: cub wont start

Postby rjohnson » Mon Mar 09, 2015 10:48 am

Cylinders are 1, 2, 3, & 4 starting from the fan and going towards the flywheel. I agree with timing being off. The number one cylinder should be marked on the cap, although it sounds like your plug wire order is correct. The magneto (or distributor) timing can be fine tuned by loosening the bolt and adjusting the magneto/distributor to either advance or retard the timing. This should help with your backfiring although it could be your carb causing issues as well.

brianc1471
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Zip Code: 27344

Re: cub wont start

Postby brianc1471 » Mon Mar 09, 2015 11:02 am

[
Attachments
Farmall Cub Firing Order.png
Here's a quick drawing to show how I've got it. I think it's correct, but I could be wrong. What could I have done that would cause the tractor to get out of time, if the plugs wires are correct?

kluf357
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Re: cub wont start

Postby kluf357 » Mon Mar 09, 2015 11:45 am

I would check to make sure all the plugs are firing next make sure the order is correct. It could possibly be the valves might be out of timing. Check there lash is .013in for both the intake and exhaust valves at Top Dead Center using a feeler gauge. I have found this the issue in many of my tractors. good luck with getting her running.

rjohnson
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Re: cub wont start

Postby rjohnson » Mon Mar 09, 2015 5:06 pm

I believe I misconceived what you were saying at first. The Cub only backfired after you did the work and tried the starting fluid? In this case, your firing might be 180 degrees off. This could be due to someone installing the magneto/distributor 180 degrees off. While your firing order is what it technically should be, maybe try advancing each plug wire 2 spots clockwise from where they are now on the cap.

brianc1471
Posts: 4
Joined: Mon Mar 09, 2015 8:40 am
Zip Code: 27344

Re: cub wont start

Postby brianc1471 » Mon Mar 09, 2015 7:07 pm

I set the timing when I got home today and she fired right up! Thanks for the help!


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