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Cub Loses Power while cutting grass

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49Cub2017
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Cub Loses Power while cutting grass

Postby 49Cub2017 » Tue Apr 18, 2017 12:18 pm

This started last grass cutting season. Cub runs fine and then starts acting like it's fuel starved. It continues to run, but with much less power and if I just let it run like that after about 30 seconds or so it usually starts running ok again. I've replaced the fuel bowl assembly and fuel line, and that didn't help. I notice it doesn't usually start doing this until after it's been running awhile and is hot. So now I'm starting to suspect it might be electrical. But, if that's the case, why does it sort itself out if I just let it continue to run? Could this be either a bad coil or regulator? I have noticed that if I pull on full choke while it's doing this it sometimes runs better. So that suggests a problem with the carb. I just don't understand why it's an intermittent problem. I does seem to be happening more and more often and so does seem to be getting worse. When it first started it might happen once or twice in a 2 hour run, but now it's more like a dozen times and is really starting to get aggravating! Any suggestions for what I might try next to fix this would be greatly appreciated!

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Bigdog
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Re: Cub Loses Power while cutting grass

Postby Bigdog » Tue Apr 18, 2017 1:24 pm

Electrical problems don't usually clear themselves. Sounds like dirt in the fuel tank or perhaps a sticking float in the carb. Another possibility is a plugged vent in the fuel tank cap.
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ShawnAgne
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Re: Cub Loses Power while cutting grass

Postby ShawnAgne » Tue Apr 18, 2017 1:51 pm

Mine had this problem last fall. I cleaned out the carb jet, and then cleaned out a bunch of caked on crud that was in the sediment bowl itself. However mine never sorted itself out. Eventually the engine would die because it was using more fuel than was getting to the motor. If you are having to choke it there is a fuel restriction problem some where.

Also when I was getting mine to run I noticed that if I had to much tension on the main drive belt it will bog the engine down. But it doesn't sound like that was the problem.
Shawn Agne

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Re: Cub Loses Power while cutting grass

Postby LRiddle » Tue Apr 18, 2017 5:02 pm

Agree with ShawnAnge. I had similar problems last year. Rebuilt the carb and replaced the fuel line and cleaned the tank. No more problem. I would lean towards crud in the tank in your situation.
Luke Riddle
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49Cub2017
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Re: Cub Loses Power while cutting grass

Postby 49Cub2017 » Tue Apr 18, 2017 8:14 pm

After reading the replies I have to agree it sounds more like a fuel problem. I don't think it's the tank though I'll check that out. The reason I say that is that I keep an eye on the sediment bowl and it stays clean. One thing I forgot to mention is that I did notice the carb leaking from the back choke lever side this morning which is a new development. Kinda surprised me, too, since I've got that new sediment bowl assembly on there now, and I always turn the valve off after I'm done for the day. So that sucker is allowing a small amount of gas to run down the fuel line and it was puddling under the tractor this morning. I think the carb has got problems, which is understandable since I doubt it's had anything done to it since new. I suspect I need a new carb or, at least, a rebuild. I appreciate the input. :D

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Re: Cub Loses Power while cutting grass

Postby LRiddle » Tue Apr 18, 2017 8:24 pm

49Cub2017 wrote: ...I keep an eye on the sediment bowl and it stays clean.

It is possible to have debris in the tank that is too big to pass into the fuel line. It can sit on the outlet and plug the flow without actually clogging the line. It can be particularly hard to diagnose too since whatever restricts the flow can clear the outlet at any moment.
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Re: Cub Loses Power while cutting grass

Postby Bob McCarty » Tue Apr 18, 2017 8:44 pm

49Cub2017 wrote: I suspect I need a new carb or, at least, a rebuild. I appreciate the input. :D

It's a rare carb that can't be rebuilt and it's a lot cheaper.

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Re: Cub Loses Power while cutting grass

Postby Glen » Wed Apr 19, 2017 12:27 am

Hi,
The needle and seat in a Cub's IH carburetor wears out after years of use, then the carb will drip out the hole made in the bottom of the front part of the carb, when the Cub is sitting.
The float height can be wrong too, it can be set when the carb is apart.
Or there could be dirt in the carb, in the needle and seat too, then it will drip if the dirt is preventing it from sealing.
A carb rebuild is not hard to do. Here is a post I wrote in a few days ago about it. The info is in 3 posts down the page. There are Cub parts manual pics of the carb there.
Below is a new needle and seat at TM Tractor you can look at. :)

viewtopic.php?f=1&t=96200

http://www.tmtractor.com/new/fl/5183fp.htm

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Re: Cub Loses Power while cutting grass

Postby outdoors4evr » Wed Apr 19, 2017 6:54 am

Is the fuel cap vent blocked? Does it start running better after you briefly open the gas cap?
Sounds like a vacuum is developing in the tank after it runs for a while.
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49Cub2017
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Re: Cub Loses Power while cutting grass

Postby 49Cub2017 » Wed Apr 19, 2017 7:48 am

It would sure be nice if it turns out to be a blocked fuel cap. I'm not near the tractor at the moment, but will sure check that out as well as looking for debris over the tank outlet.
I took a look at new carb prices...wow...a little sticker shock with my coffee this morning! I think I'll check with one of the folks here on the forum who rebuilds and see what that will be in case these other suggestions don't work out.

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Re: Cub Loses Power while cutting grass

Postby ShawnAgne » Wed Apr 19, 2017 8:29 am

Believe it or not I had a bug that had died in the fuel tank and was sitting in the fuel line intake. That was the cause of my problems along with the crud.
Shawn Agne

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Re: Cub Loses Power while cutting grass

Postby Urbish » Wed Apr 19, 2017 9:21 am

An easy test is to remove the fuel line at the carb and run it into a jar/gas can/whatever won't melt. Turn the fuel on full and see how fast it is coming out and let it run for a full minute. If it's barely trickling, you have a blockage somewhere upstream. If it runs out in a nice continuous stream, your problem is likely at the carb. If the flow slows down, remove the fuel cap and see if it resumes full force. That will indicate a plugged vent in the cap.

Jim
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kully560
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Re: Cub Loses Power while cutting grass

Postby kully560 » Wed Apr 19, 2017 1:29 pm

the gas valve should always be closed when the motor is not running ! very hard for the float to hold back that much gas when the tank is on top of it wanting to drain down . my cub and old ford always leaked when not running close gas valve when not in use.

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Re: Cub Loses Power while cutting grass

Postby Urbish » Wed Apr 19, 2017 8:56 pm

kully560 wrote:the gas valve should always be closed when the motor is not running ! very hard for the float to hold back that much gas when the tank is on top of it wanting to drain down . my cub and old ford always leaked when not running close gas valve when not in use.


I haven't shut the fuel off on my Cub in three years and always keep the tank full. I haven't had so much as a drip from it. If the carb is overflowing when sitting, either the needle and seat need to be cleaned/replaced or the float is out of adjustment.
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Re: Cub Loses Power while cutting grass

Postby Scrivet » Wed Apr 19, 2017 9:35 pm

Urbish wrote:.......I haven't shut the fuel off on my Cub in three years and always keep the tank full.........
You have been very lucky in my opinion.
Quote from the owner's manual;
It is advisable to close the gasoline shut-off valve if the engine is to be stopped for any length of time.


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