Weird starting problem

TennesseeCub · Jul 5, 2015

Hi,
My old Cub ('47 or '48) will go along fine starting instantly on the first pull. Three times now after leaving it parked for a while it won't fire at all. The first two times this happened, I worked for days cleaning plugs etc, and then by some miracle it sputtered to life and showed no sign of trouble. I'm in the middle of my third experience with this and I'm looking for ideas.

My intuition is telling me it isn't getting any spark. It has new gas. It has no air filter, the front of the carb is just open. I recently rebuilt the carb too.

I'm probably going to replace the plugs. They are a little black, but I've been cleaning them with a steel brush. I tested for spark on one and it was there but seemed kind of weak. It's hard to believethe re is anything wrong with the electrical other than the plugs because it will start and run so well for long periods and only gives me troubles after I park it for a while.

Any ideas? Thanks in advance.

Kevin

Russ from MN · Jul 5, 2015

Have you cleaned the points?

Steve@Advance · Jul 5, 2015

Need to catch it in the act, check for spark when it won't start. Points would be a good place to start.

Definitely replace the plugs. If they've been wire brushed, they are likely damaged. Might step up one heat
range if they're running black.

Ted in NE-OH · Jul 5, 2015

Do you turn the gas off when not in use. The needle valve may leak and flood the engine.

old · Jul 5, 2015

Spark needs to be a blue white in color and jump a 1/4 inch gap or more. If it is not that good you have dirty points or bad points. No air cleaner is not good at all and is asking for engine problem sooner or later

Cory Schmidt · Jul 5, 2015

Battery ign. or Mag.? If mag I can't help other then maybe check coil.

If batt. try throwing the charger on it for a while when it don't start. Your battery may be gone or on way out. Have that problem with a W4, Case SC, and Farmall C. My nephews got on them left switches on, I'm too cheap to get new batteries. You can run them all day, start fine if ran everyday. Leave them sit a couple days toss the charger on or crank all day and get nowhere. The Case is the worse cause if you stall it(not hit the switch) it will not go till a charger is put on. If you hit the switch it will go all day, and start fine.

T.R.K. · Jul 5, 2015

How old is your gas?
Do your sparkplugs have a grey coating on the insulator when you remove them? That grey coating comes from running old fuel and it is conductive, so your spark is probably following the insulator to ground.

Janicholson · Jul 5, 2015

A wire brush should not be used on plugs, the steel in the brush abraids off onto the insulator causing a short to ground. Run it with an air cleaner to keep it running, and reduce plug fouling. Is the impulse coupling clicking? Jim

Weird starting problem

TennesseeCub

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Russ from MN

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Steve@Advance

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Ted in NE-OH

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old

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Cory Schmidt

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T.R.K.

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Janicholson

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