Re: Decisions to make about the '50 Cub

Fri Mar 27, 2015 12:36 pm

The reason I decided to go ahead and rebuild the magneto is because my spark has been inconsistent with the external coil modifications. It has been very hot at the coil, but weak at the plugs. And, since the PO did a lot of what I would call "unorthodox" repairs, I have decided to go ahead and start fixing things right on this tractor.

Honestly, I had continued to do the same type of patchwork repairs to the tractor that the PO had done because I needed to keep the tractor working. Well, that finally fell through for me because it came plow time this year and the tractor wouldn't even start. So, the other day my neighbor brought over his Kubota and tilled up all my gardens for me instead! It turns out that his box tiller does a better job than my plow and disc harrow does.

So, now that I'm not under any time pressure to get this cub up and running, I'll just go ahead and start fixing everything right from here on out. It's had enough patchwork. It deserves quality work, so that's what I'll do.

Thanks for the encouragement! I appreciate it!

Re: Decisions to make about the '50 Cub

Thu Apr 02, 2015 8:20 pm

Today my tractor finally got FIXED! I replaced the distributor cap, rotor, plugs, and plug wires with good old AMERICAN made stuff from TM Tractor, and it roared to life effortlessly!! :{_}:

For the first time in a long time, I had some good seat time today too! I ran it for a couple of hours and it performed flawlessly!!!!

I'm finally back in business with the cub! So, now I can use it, and keep bringing it back to its former self. :{_}:

Yes, I'm happy!!!

I want to thank all of you folks for chiming in and offering advice and helping me figure this all out! Thank you again so much!

The next thing on my list is to rebuild the magneto and get it off the external coil. But, for the meantime, the external coil is working great! It has tons of power, and just keeps on pulling my hills with no problem. I'm impressed! It has never had so much power before! And, it will start with the hand crank, which is something I could never get it to do before. :D

Re: Decisions to make about the '50 Cub

Thu Apr 02, 2015 8:26 pm

It's a great feeling and thanks for sharing your well-earned excitement. :{_}:

Re: Decisions to make about the '50 Cub

Fri Apr 03, 2015 5:55 am

You did good, lots of enjoyment to follow :{_}: :{_}:
Donegal Cub.

Re: Decisions to make about the '50 Cub

Mon Apr 06, 2015 5:22 pm

I cannot say enough how good it is to have my cub running again. Thanks again to everyone who helped in any way whatsoever!

I had intended to pull it in the garage back in January to do a little sprucing up on it. Well it turned out that it got some attention for sure, but not what I expected! Last year I had adjusted the valves, and that helped a bunch, because it just ran like it was tired until I adjusted them. But, just to be sure, I checked them again recently. When I removed the manifold, I found that I had not tightened the manifold bolts tight enough, and it was barely getting enough vacuum to make the carburetor updraft. So, that got corrected.

Then, after observing a weak and intermittent spark, and discovering the magneto was saturated with oil inside, I cleaned out the excess oil, and replaced the external coil, points and condenser, rotor, distributor cap, plug wires and spark plugs. Now it has a good hot spark just as it should! 5 years ago I had replaced a lot of that stuff with poor quality stuff, and I've learned that the cheap stuff is just that, CHEAP! My advice to anyone is, go ahead and buy the good stuff! You'll probably only have to buy it once.

Also, the rubber fuel line and original fuel strainer got replaced with a new strainer and metal fuel line. I also bought new rubber hoses for the air intake and replaced the carburetor gasket and used Indian Head Shellac on it. Now, the cub runs better than it ever has.

And today my magneto puller tool arrived from Earl, so when I get the money to buy up the rest of the magneto parts, I'll finish rebuilding it, and be putting it back on a fully functioning magneto.

I'm just documenting all this for myself, and anyone else who is struggling with a sick or poorly maintained cub. I've got a long way to go, but at least with it running, I know it will eventually get back to what I want it to be! :D

Re: Decisions to make about the '50 Cub

Fri Jul 24, 2015 7:59 am

Well, the cub has done so good this summer that I've mainly been lurking and not posting. It's been a very busy summer as usual.


Last Saturday the cub started doing the exact same thing it did last fall. I took it out to do some bush hog work and all at once it spit, sputtered, had no power, and wouldn't stay running. I had to tow it with a pickup truck to get it back to the barn... :?

I took the plugs out and they were covered with soot. I cleaned them and at least it would start again, but had no power to even pull itself. It would spit and sputter, then roar back up, but never reach a decent RPM, and when I'd try to move it then it would die and be very hard if not impossible to restart.

I never had any problems like this until I adjusted the valves a couple years back. Is it possible that I have one sticking? I've replaced the carburetor, fuel line and strainer assembly this past spring, and completely rebuilt the ignition. It was doing so good too. Man, I am SO disappointed... :(

I need my tractor and I can't figure out why this keeps happening.

Re: Decisions to make about the '50 Cub

Fri Jul 24, 2015 9:29 am

It's unlikely that the valves are a problem, if it was running good and you were working it. That's typically what keeps the valves working good, a bit of hard work on the machine keeps the engine running hot and the gasses moving fast, so less carbon buildup in the valves. It really sounds like either a fuel issue, or a spark issue. I'd lean towards fuel since that's the easiest point of entry for contaminants in the system. Do you store the tractor outside? Could it have water in the gas tank? It's been raining a lot, and it could be just enough condensation (from the hot/cold/humidity/etc) could have built up and finally gotten into the system. Is there rust in the tank and plugging up either the screen at the fuel bowl, or worse, the screen in the carb? That would be my next check. Next it's the fuel flow and the needle seats in the carb to check. If the fuel system all checks out, and there's lots of fuel flow through the carb, and it's still not running good, then it's likely a spark issue. Get back to checking the timing on the mag, plug wires, etc. It's possible that the timing could have gone out if you hit a bad bump and something was loose. Anyway, those are my thoughts. I'm sure others will chime in. Good luck!

Re: Decisions to make about the '50 Cub

Sun Jul 26, 2015 3:09 pm

If you are going to rebuild that magneto - suggest you look at Mainely Magneto's .. they are very reputable both for parts and for rebuilding. Also, if you want to save a little money .. the J4 mag coil from eBay .. usually aftermarket .. the name escapes me at the moment .. but prices start around $59.00US and can go much higher .. patience is the key ..

Re: Decisions to make about the '50 Cub

Sun Nov 29, 2015 3:01 pm

Thanks to the wisdom and patience of many of you folks, my 1950 post-demo cub is running and working better than it ever has! :{_}:

Now, when it idles, it is extremely quiet, and sounds like a well oiled sewing machine. My problems I'd been having were caused by some severely fouled new spark plugs. It turns out my oldest son had flooded the tractor out really bad, and when I was trying to remedy that I got to chasing other problems created by the plugs lack of ability to properly fire. I should have checked them better.

Anyway, I want to say a big ol' THANK YOU to everyone who has pitched in to give me some advice, supply parts, and sold me the implements and such to make my cub a great machine. All I need to do to make it ready to teach my other two boys some tractor driving skills is fix a non functioning brake on the left side. While I have it apart, I'm going to have them help me rebuild that final drive.

I do need to get some slop out of the governor, but since it's running so great I'm willing to leave it well enough alone for the meantime.


Re: Decisions to make about the '50 Cub

Fri Dec 04, 2015 11:33 am

Glad your Cub's doing better. You've been through the mill with your ignition issues! Which plugs are you running? If they should carbon up again in the near future I would consider hotter plugs, especially if you're not working the engine very hard. Usually if the plugs are too cold, in my experience, they will load up pretty quickly.

Re: Decisions to make about the '50 Cub

Sun Dec 06, 2015 8:21 am

I was running Champion D-21 plugs, which as I understand it is the hotter plug recommended. I think a lot of my problem was actually being created by carburetor issues flooding the tractor and fouling the plugs. Since I put the new carburetor on with a set of new plugs, it hasn't done it since. My factory carburetor was damaged by someone's jury rigging, then when I tried to fix it I cracked the main jet inlet, letting gas seep in straight out of the bowl, and all my attempts to remedy that failed. So, I ended up getting a new carburetor that was "supposed" to be ready to go out of the box, but was drastically out of adjustment. I should have checked it first. That was my fault.

Yesterday son #1 got about 30 minutes of good seat time running the cub and it did just fine. I believe we got it figured out, finally!!!

But, I will keep an eye on these plugs to see if I have any more issues with them. Thanks!

I do have some slop in the governor that needs to be addressed at some point in time, but not yet. I tried to adjust it per the service manual, and it has a lot of loose movement. It can wait for now. It's running and doing good, so I'm not monkeying with it right now.

Re: Decisions to make about the '50 Cub

Sun Dec 06, 2015 1:16 pm

Ben B wrote:I was running Champion D-21 plugs, which as I understand it is the hotter plug recommended. I think a lot of my problem was actually being created by carburetor issues flooding the tractor and fouling the plugs. Since I put the new carburetor on with a set of new plugs, it hasn't done it since. . . .

A hotter plug won't have any particular advantage unless it has the chance to actually warm up in a running engine. You are correct that flooding and similar problems while trying to start an engine will foul the plugs even if they are a high enough heat range. There are hotter spark plugs than D-21s, but I have yet to hear from anyone with a Cub that actually benefited from them.

Re: Decisions to make about the '50 Cub

Sun Jan 17, 2016 1:17 pm

I'm gonna go out on a limb here and say that the cub is finally fixed engine wise. It starts every time, and has plenty of power.

So now, I can finally start to concentrate on the other things it needs. That would be a new transmission casting, an inspection hole cover, a bottom bolster casting, and a front axle tube.

I guess I better get started shopping, huh? Now that it is running good, I may try to head to Boss's cubfest this spring. I ain't ever been, and I'm ashamed of myself for that... :(