Plugs Foul Sometimes, Won't start

I've fallen into a routine of having to pull the plugs to the '49 8N, cleaning with carb cleaner (tips are oily and carbon covered) in order to restart. Sunday, I went through the routine, got it started, then looked up what setting the carb should be (it was backfiring). I read to turn main carb adjustment all the way in, and two turns out. Ran fine for 7 gallons of fuel (all day mowing and discing). When she quit, I realized fuel was low, it was a long hard day, and I had done much and it was getting dark, so I shut off fuel petcock, disconnected battery and ran an extension cord to the trickle charger for the night (quit near barn).

Next afternoon, filled her up and pulled a plug. The plugs were gorgeous (no carbon, no fouling, perfectly clean). I tried to start and she fired one two three but wouldn't catch. I pulled plugs and now they were filthy again.

I pulled and cleaned 3 more times and even used starter fluid. Each time I pulled, they were black, oily and filthy again. Gave up for the afternoon. I'm stuck in a catch-22. When clean, it will fire on a couple of cylinders, then only on the first turn when I restart. But it can't put together one whole rotation. It keeps overrunning the starter so you have to wait til starter stops to reengage and try again. BIG PIA! Gaps are at .025" and plugs were installed new a few weeks ago. Suggestions?

if they go from perfectly clean to oil fouled in just a couple pops and revs.. you are pumping oil badly!

the starter catch and over run is from it trying to start, momentarilly going faster than the starter, letting the drive kick back, and then dieing out. a newer clutch or follow thru style drive will help that.. but the catch and die is linked more to not starting problems deeper in the engine, IE. valves, dry, wet compression and oil control... overall engine health stuff.

I'd wager with oil pumping that bad, you could not do a dry compression reading..

I'm willing to limp along and re-ring during the winter. Dad had this engine completely rebuilt (bearings, valvejob, etc) only a few year before he passed. He used it for mowing only. He couldn't have put more than 300 hours on it in that time. It may have been (hopefully) that the rings never seated properly.

I wonder if changing oil to a much higher viscosity will let me limp along all summer?

I'm just too buried in too many projects to have to disable this tractor and rebuild right now.

Are they oil fouled or fuel fouled? It is real easy to flood these engines. One of mine will flood in a heart beat. How is the spark? when was the last time you installed new points? I installed the new style bendix and like it a lot better, mine used to do the same as yours with the old style bendix.

Some say two turns open and leave it, I like to fine tune it a bit more. I start at 2 1/2 then with it running at working rpm, I adjust in until it just start to falter and then back it out 1/4 turn. then see how it runs with a full load and adjust from there.
Good luck

Brian,Put some of these anti foulers on the spark plugs that keep fouling out to keep it hitting on all four till you can overhaul it.You can find them at OReillys Dorman Help! - Non-Foulers
Part # 42009
Anti Foulers

Black with Carbon which wipes off pretty easily. Very wet. (almost slimy) Gasoline in my opinion wouldn't leave that kind of film, so I'm guessing
it's oil.

I ran the tractor pretty hard for that work day and she started heating up pretty good under load.

Points are new this December and pulled with gap checked twice since and good. Coil is new, Condenser is new.

Brian,You might also change the oil to a 20W50 to help some.Does it smoke quite a bit when running on all four cylinders?

I'll try it.. hope it will meet the clearance under the fuel tank.

Thanks

Yes they will fit under the tank

Given that your dad rebuilt it and you did seven hours work with shiny clean plugs afterward . . . I'd be thinking like R. Geiger's advice. Incorrect fuel mix or not enough consistent bright spark to keep the plugs from getting carbon fluffed up.

If you are running 30 or 10W30, I'd go 15W40 before last resort 20W50.

Oh and timing . . . Backfiring through the carb can mean too advanced; through the exhaust, too retarded.

When you pull an "oily" plug, is it wet with unburned fuel or wet with crankcase oil?

If it only has 300hrs on a rebuild, run the snot out of it and see if it improves

Sound Advice

The reason the plugs were shiny clean, was the 7 hours of hard work. The rings must be in great shape, as in well mated to the walls, for the plugs to be that clean! Good valves too.

But don't use heavy oil in your probably very healthy rebuild!
Work it hard some more with 10W30 or 15W40.

But even though it puts out clean under load, adjustments are still in order.

Sounds like it is flooding. The gas is not vaporizing/igniting and accumulating on the plugs. Weak spark and/or over rich mixture would be what I would be looking at.

Ya, that would explain why it only burns clean under load and higher rpm.

I used a Mapp Gas torch yesterday to clean the plugs..Much more thorough than carb cleaner and abrasives. Works in seconds.

I regapped the plugs after at .024" and it did the trick to restart. It makes sense that it's probably running too rich. It was backfiring almost constantly yesterday from about an hours' run time (raking and grading my garden). I played with the idle and mixture jets. With throttle open, the mixture changes didn't seem to make any difference. I haven't touched the carb short of draining the sediment bowl on occasion to get things started with fresh gas.