Farmall Cub

I like to periodically start EVERYTHING in the shed and let it run for 30 minutes or so, every month, during the winter. I think its a good thing to keep batteries up, things oiled, and gas moving around a bit in the carbs and run long enough to get the moisture out of the engine as best it can. Yesterday, I fired up 8 tractors, three small engines, 5 lawnmowers and one hit and miss engine. Everything ran fine EXCEPT one cub, which had a distinct miss. A few seconds with a long, well insulated screwdriver quickly identified #1 cylinder as the culprit. Its a completely rebuilt engine, and I immediately figured I had a fouled plug. Pullled the plug, bead blasted it, reset the gap, and stuck it back in. Still had a miss............Hmmmpf. Pulled it again, and swapped it for another plug I had in a drawer. Still missing. Double Hmmmmpf. Okay, I may have two bad plugs. Swapped the FIRST plug for #4 plug, which I knew was firing fine. Still have a miss.... and its still #1.
Okay... maybe a mag cap issue. It was an old cap, after all. Perhaps a carbon track. Pulled the cap, and inspected it. Nothing of note. Swabbed it out and reinstalled. '
Still missing.

Looked around on the shelves and found a new cap. Installed it. Same problem. AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAG>!
Put the old cap back on. This time, when I cranked it, I got a HUGE BANG backfire, which squirted a bit of oil out of the airbreather cap.

I was positive the timing was correct, but now I began to wonder.
I disconnect the mag center wire, (and have the kill switch doing its thing too) and have #1 son crank (by hand) the tractor over while I feel for compression in #1 to bring #1 to tdc and ck timing....what a surprise I found.

Now, remember, this is a rebuilt engine. New valves, guides, pistons, bearings, seals, the works. It NEVER occurred to me it could be a mechanical problem, but now, it was undeniable. As #1 son cranked #1 piston, I felt NO compression or intake on #1.
At this point there are two conflicting feelings going on.

1. I'm happy I've discovered the problem, suspecting strongly a stuck intake valve.
2. Worried, wondering how badly stuck it was.......

Two bolts out, one valve cover removed in about 2 minutes reveals that yes, the #1 intake valve is stuck. It took about 30 seconds with a screwdriver to loosen the valve back to working condition.
2 more minutes to reinstall the cover and another minute to put the #1 plug back in and snap the wires back in place..
30 more seconds to choke, crank, unchoke, and crank again and Voila"... it ran perfectly.

Added a touch of Marvel Mystery oil to the gas... can't hurt.
Lesson learned.....

I read this forum regularly, and in a recent posting by one of our members who shall remain anonymous at this point in time, could not get his cub to start and tried everything he knew (and he is quite an expert) and in desperation he checked the fuel tank, GUESS WHAT!!. So don't feel so bad if it can happen to him it can happen to anyone, LOL.
Donegal Cub.

I'm the same way, I like to start everything thru the winter also. Especially with this ethenol gas it good to keep some fuel goin thru the carbs. Glad you got it fixed easily.

Seafoam is an amazing product to prevent and remedy stuck or sticking valves. The fuel these day is really poor and does not have any shelf life before situations like yours happen. I have had the same scenario and used the seafoam which was recommended by a boater friend. add seafoam to the engine oil and the fuel tank to prevent fuel varnish.

Sgtbull, glad you could diagnose and fix the problem that easily!!!

Donegal Cub wrote:I read this forum regularly, and in a recent posting by one of our members who shall remain anonymous at this point in time, could not get his cub to start and tried everything he knew (and he is quite an expert) and in desperation he checked the fuel tank, GUESS WHAT!!. So don't feel so bad if it can happen to him it can happen to anyone, LOL.
Donegal Cub.

I've done the 'out of gas' thing too many times...that's pretty much the FIRST thing I ck anymore:) In fact, with gas being so crappy these days, I rarely keep it in the tanks anymore, A very important piece of equipment in my shop now is a 4' length of 3/8" hose zip tied to a 18" wooden stick. I do a lot of "robbing Peter to pay Paul" at my place, siphoning gas out of one tractor to run in another. Its much faster than using a carb drain.. you can get a lot more gas through a 3/8" hose than through a 1/16" needle valve! After I've run everything for a bit as I just did, I drain the tanksand it all goes into something I'm using regularly, like my atv, truck or the JD 70 w/ the snow blade on it. Believe me, the 70 likes the extra gas, and needs it.

sgtbull wrote: Believe me, the 70 likes the extra gas, and needs it.

Have an old '38 G. I understand this statement all too well.