Cub running issue.

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kcsharp
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Cub running issue.

Postby kcsharp » Fri Jul 01, 2022 3:57 pm

Hello all,

I was using a cub to start a garden spot this year. Ran fine ever weekend for about 2 months getting the ground prepared then one day it acted as though it was running out of gas (it has fuel) and died. It has not really ran right since then. I've tried cleaning and replacing carb, replaced plugs, has spark, its getting fuel. I got it running twice, once a couple a weeks ago and made 2 cultivating passes and again it died (again as it sputtered like it was running out of gas).

This morning I got it to fire up, let it idle for about 5 minutes, then got another 5 minutes of driving it around and the same thing, sputtered and died. It will usually start up (I hand crank it so when I'm fresh it starts) and run for a several seconds and die.

Looking for what is causing this or a trouble shooting guide as what to do to get this thing running.

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Re: Cub running issue.

Postby IHPWR » Fri Jul 01, 2022 4:17 pm

when did u check for spark? after it died or after it had sat for a while? Color of spark? Might be coil or condenser. Need to narrow down whether a ignition or fuel issue

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Re: Cub running issue.

Postby muleboss » Fri Jul 01, 2022 4:43 pm

Sounds to me like you have junk in gas tank. Clean it.

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Dale Finch
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Re: Cub running issue.

Postby Dale Finch » Fri Jul 01, 2022 6:28 pm

It also sound like a fuel issue to me...

With it not running, I would rock the tractor side to side while looking into the gas tank (with a good flashlight) to see if you can see any floaters or particles that might be clogging the top inlet of the sediment bowl. If nothing, remove the glass bowl along with the gasket & screen. Clean if dirty...you might need a new gasket.

Then move down to the inlet at the carb...remove the fuel line & see if the tiny inlet screen deep down in there is blocked with anything.

Next, remove the brass hex head main jet and spray it (carefully away from you!) with carb cleaner.

Those steps should at least eliminate some things without costing anything.
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Re: Cub running issue.

Postby Eugene » Fri Jul 01, 2022 6:51 pm

Coil. Swap out the coil with known good one.
I have an excuse. CRS.

kcsharp
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Re: Cub running issue.

Postby kcsharp » Fri Jul 01, 2022 9:06 pm

I'll see what the gas tank looks like on the inside. It has a small inline filter that looks to have good clean gas in it so I just assumed the tank was clean.
It runs without a battery via magneto so I'm not sure it has a coil, correct me if I'm wrong.

Another issue. It has a starter but it does not crank. I just swamped a known starter that works and still no crank, the one that didn't work on this cub worked on the other. I'm assuming I've ground out somewhere??? It reads 6V on the multimeter when connected to the positive on the battery terminal and the wire on the starter nut.

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Re: Cub running issue.

Postby Don McCombs » Fri Jul 01, 2022 9:50 pm

Your magneto has an internal coil.
It's possible that your starter is not adequately grounded. Remove and clean ALL connections in the starting circuit, including the battery and battery ground.
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Re: Cub running issue.

Postby Eugene » Fri Jul 01, 2022 10:29 pm

kcsharp wrote:It runs without a battery via magneto so I'm not sure it has a coil, correct me if I'm wrong.
OH! it has a coil, inside the magneto.
I have an excuse. CRS.

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Re: Cub running issue.

Postby Dale Finch » Sat Jul 02, 2022 7:03 am

kcsharp wrote:I'll see what the gas tank looks like on the inside. It has a small inline filter that looks to have good clean gas in it so I just assumed the tank was clean.
.....

You need to make sure that that inline filter is designed to be used for GRAVITY FEED, not with a fuel pump. If you are not positive, you might try replacing it with a new one...one designed for gravity feed such as those sold for lawnmowers, etc.

Also, make sure it is installed in the CORRECT DIRECTION...look for an arrow showing fuel flow direction. (The shape of most inline filters makes direction a tad confusing.)
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Re: Cub running issue.

Postby kcsharp » Tue Jul 05, 2022 8:06 am

Changed out the battery cable going to the starter so that works now! Way easy than hand cranking it!

I got it to run a little bit and it started acting up again. The gas tank looks clean to me, not rust flakes or anything stuck in there as far as I can tell. I did have the in line filter on backwards and could not get gas flow through it so I by passed it to see if that helps. It started and ran fine for about 2 minutes, was above to move it about 20 feet before it sputtered and died.

I'm going to link 2 youtube videos and maybe this will help.

https://youtu.be/UvHhHwI8Pfg

https://youtu.be/UvHhHwI8Pfg
Thanks guys!

kcsharp
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Re: Cub running issue.

Postby kcsharp » Tue Jul 05, 2022 8:07 am

Here is the second video

https://youtu.be/5h_LomfWe2Q

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Re: Cub running issue.

Postby Gary Dotson » Tue Jul 05, 2022 8:31 am

That has the sound of a bad condenser.

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Re: Cub running issue.

Postby indy61 » Tue Jul 05, 2022 11:34 am

Remove inline filter and blow all the way into fuel tank.
Reinstall clean inline filter and remove bottom drain plug on carb to ensure you have steady flow for a minute.
Remove and clean main jet from side of carb.
Make sure you have plenty of fuel.

meteringjet.jpg

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Re: Cub running issue.

Postby kcsharp » Thu Sep 22, 2022 10:06 am

Now that it’s not 100 degrees outside I’m ready to tinker with this again. Still no improvement, will start and run for 10 secs and die. I do not believe it is a fuel issue or carb issue. Plenty of gas coming in and out and I put the carb on another tractor and it ran fine.

Should I start with new plugs and condenser? Coil??

Thanks guys

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Re: Cub running issue.

Postby Glen » Thu Sep 22, 2022 6:35 pm

Hi,
The gas strainer under the gas tank might need cleaning, if it hasn't been cleaned lately.

You didn't say the year of the Cub.

Below is a page from the 1949 Cub owner's manual showing the strainer.

http://farmallcub.com/rudi_cub/www.clea ... age-25.jpg

There is a screen above the gasket, it may be dirty, and slowing down the gas flow.
The screen can break from age, and not filter the gas.
Sometimes the gasket won't seal if you try to reuse it.
TM Tractor has a new gasket and screen.
Below are the listings.

http://www.tmtractor.com/new/fl/426fp.htm

http://www.tmtractor.com/new/fl/235fp.htm

It is easier to get to the strainer if you move the Touch Control arms to the rear or down position before working on the strainer.

Here is other info below, maybe you know it already.

You could do a gas flow test, and see if enough gas is getting to the carb.
Be sure the gas valve under the gas tank is fully open.
Use a large clean can, or glass jar, to catch the gas.
If you use a clean can, or jar, you can put the gas back in the gas tank when done.
Remove the small plug on the bottom of the carb, the originals I have seen have a square head.
Catch the gas.
The 1st gas that comes out will be what is in the carb, then the gas flowing from the gas tank.
The gas flow should be steady, and not stop, and be about a pencil size flow.
Catch the gas for about 1 minute, then put the plug in.

If the flow is good, the screens are probably ok, unless the screen in the gas strainer is broken.

If the flow was too slow, or stopped, look at the carb inlet screen, but you said the carb is new, I think, and the other info below.

Like Dale said above, if it has an inline filter, it has to be for a gravity feed system.
They have said on here that a filter for a system with a gas pump can slow the flow.

The gas tank should have a vented cap, and the vent holes need to be open and clean.
If the vent is plugged the gas flow will stop in a few minutes with the engine running.
The engine is stopping sooner than a plugged cap vent would usually take to stop the gas flow, but you could check it.

They have said on here that some of the new foreign made replacement carbs have the float level set wrong, then the engine doesn't run right. The float needs setting when new.
But you said the carb worked good on another tractor.

You could look at the spark plugs, they should be clean and not fouled.
The manual says the gap should be .023".

The ignition points and condenser need filing or replacing every 250 hours of use, the 1949 Cub owner's manual says.
The points burn more the longer the engine is run, eventually they get so the engine doesn't run right.

Below are pages from the 1949 Cub owner's manual telling about the points.

http://farmallcub.com/rudi_cub/www.clea ... age-30.jpg

http://farmallcub.com/rudi_cub/www.clea ... age-31.jpg

I change the points with the magneto on the engine, then you don't lose the timing.

Below is a listing at TM Tractor for new points and condenser, you can look at the pics.

http://www.tmtractor.com/new/el/367fp.htm

To change them, you need a short screwdriver, with a sort of wide blade, and an 11/32 open end wrench, for the nut holding the end of the point spring.
I sit down next to the engine, on a lawn chair, and use a good light. You can put a large towel on the ground, to catch any screws that might drop.
Or you can file the points flat, if they aren't burned much. Wipe off all filings with a clean cloth.
The nut at the end of the point spring only needs loosening some to remove the point, there is a slot in the point spring on the ones I have seen, so the spring slides out with the point.
Tighten the nut gently, there is an insulation in the side of the magneto, it can break if the nut is tightened too much.
The point gap is .013" the Cub owner's manual says, for a magneto.
You need a flat feeler gauge to set the point gap.

The condenser could be bad, like was said above.
The engine won't run right with a bad condenser.

The original coils in Cubs commonly quit, some work for a few minutes and quit, then work when cool again, some quit completely.

Here is info about checking the power of the spark, if you need it.
You could do a spark test and see if the spark is good, or not enough.
Remove the center spark plug wire from the distributor cap, hold it by the insulation with the metal end about 1/4" from a bare place on the engine.
Put the transmission in neutral, turn the ignition switch to on, and run the starter. The spark should be blue or white, and jump the gap. A yellow spark is weak, and needs improving, the engine may not run.
I would charge the battery fully before doing the spark test.
Be sure the Cub doesn't roll when sitting in neutral.

Below is a listing at TM Tractor for a new magneto coil. It is under the cover on top of the magneto.
If you replace the coil, there is a rectangular bar through the center of the coil for mounting, save it and reuse it in the new coil.

http://www.tmtractor.com/new/el/713fp.htm

The ignition timing is important also, if it is off some, the engine may not have as much power as it should.

Below is a pic of the points and condenser in the magneto. :)
Attachments
Cub magneto 8.jpg
Cub magneto 8.jpg (25.14 KiB) Viewed 336 times


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