Cub Cutting Out under a Load

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Cub Cutting Out under a Load

Postby jpate831 » Fri Jun 20, 2014 8:20 am

Hey Guys!

My '47 Cub's been acting up for a while. It runs smooth as silk at low, medium, and even high idle speeds. But when I put it under a little load, like maybe engaging the mower deck while crawling a slight incline, it starts cutting out and will eventually die if I don't stop it and lower the throttle considerably. I've been looking at the engine troubleshooting page and trying to rule out a few of the possible causes. So far, I have:

Replaced the coil.
Cleaned the main jet in the carb.
Checked the air cleaner.
Inspected the distributor cap and contacts.

Nothing that I've done so far has helped. What say ye experts?
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Re: Cub Cutting Out under a Load

Postby Eugene » Fri Jun 20, 2014 8:36 am

First thought, partial restriction in the fuel system, limiting the fuel flow. If it's a fuel flow problem the stumbling should show up perhaps 30 seconds after applying the load. Engine should have plenty of power for the 30 seconds or a bit more time until the fuel level drops in the carburetor.

Second thought, low compression. Suggest a complete engine tune up including compression tests. Complete tune up will correct a slight ignition timing problem.
I have an excuse. CRS.
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Re: Cub Cutting Out under a Load

Postby Connecticut Calvin » Fri Jun 20, 2014 9:34 am

jpate831 wrote:Hey Guys!

My '47 Cub's been acting up for a while. It runs smooth as silk at low, medium, and even high idle speeds. But when I put it under a little load, like maybe engaging the mower deck while crawling a slight incline, it starts cutting out and will eventually die if I don't stop it and lower the throttle considerably. I've been looking at the engine troubleshooting page and trying to rule out a few of the possible causes. So far, I have:

Replaced the coil.
Cleaned the main jet in the carb.
Checked the air cleaner.
Inspected the distributor cap and contacts.

Nothing that I've done so far has helped. What say ye experts?


I am by no means an expert, but the experts here gave me the guidance that I needed to fix my problem last year which was just as you described. My governor linkage was not properly adjusted and the governor was never able to compensate for the loads. Just like you, going up a slight incline my engine would die just as it did when I raised my front blade. Try this: with your Cub at 1/3 throttle, grab the linkage connect from the carb to the front of the tractor and give it a slight forward and backward push. You should feel some resistance as the governor tries to adjust against you. If not, that's probably your problem. Check the manual...the necessary adjustment process is pretty clear. Hope that helps!
She thinks my tractor's sexy...
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Re: Cub Cutting Out under a Load

Postby jpate831 » Sat Jun 28, 2014 10:17 pm

Well, it's fixed.

When I first restored the Cub, it had a flooding problem. It would flood, and gas would leak out of the breather side of the carb. But when it was running, it ran great, even under a load. Last year I "fixed" the flooding issue by adjusting the float. This immediately took care of the leaking, and I thought all was well. Unfortunately it died on me 3 or 4 times after that in the parade last year. At the time I assumed it was bad gas or something. But I didn't connect the two issues until yesterday. Every time it died in the parade, it was also under a little load going up a hill, pulling a trailer full of riders, etc.

Anyway, I readjusted the float today, and I think I found the sweet spot. It runs great under load now, and it doesn't flood or leak.

Once again, I have met the enemy, and he is ME!!

Thanks Guys.
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