super a runs bad when warm

pork · Oct 16, 2013

paps super a was restored and overhauled 10 or 12 years ago. it has ran great till last year then got worse this year. we use it to cultivate 25 acres of tobacco 3 or 4 times each year. when you first start, it will run like new in third gear. as the engine comes to temp, it looses power and must drop to second. about 30 min later, it has to go down to first and will hardly pull itself. there is no steam from radiator or water loss to speak of. there is a lot blowby out the oil fill cap and hood has oil residue from this. it starts instantly. I have checked timing, done plugs, coil, points, condenser, cap, button. I think its the rings, whats you idea. thanks

gene bender · Oct 16, 2013

You forgot the compression check

Janicholson · Oct 16, 2013

Dose it restart easily when t is running poorly? Does it idle down without stopping when in the stage of poor power? Does it run smooth or misfire and buck? If it does not do these things, it could be a drive train or brakes hanging up causing power loss. With implements out of the ground, and running in second gear will it coast a ways or does it seem to stop suddenly? Jim

pork · Oct 16, 2013

it is real hard to start when things start to happen. it doesn't jump and buck, but it does sound like a miss. my first thought on the miss was to pull plug wires while running and see which cylinder, however each cylinder makes it really miss. so, they are all firing. I don't think its a brake hanging cause I don't smell anything. it will idle fine even when hot. also, if you run it at say 1/3 throttle and not wide open, it will lug in second most of the day. when its wide open, things go downhill fast. I hadn't thought of a comp test, oops. but without putting it in the dirt and getting hot, I may have trouble testing.

Phil Tibbetts · Oct 16, 2013

Have you checked the coil and condenser?

Janicholson · Oct 16, 2013

Check the fuel cap for a plugged up vent hole. Even partially plugged will cause the issue. Mu guess is restricted fuel. Running at slower RPM draws much less fuel and it can then keep up.
Put a lawn mower tank on a carpet strapped to the fuel tank. Run a rubber (fuel) hose to the carb (fitting and clamp needed to adapt the line) then run it to see if it stil happens. Jim

pork · Oct 17, 2013

I thought of that early on. we ran cap loose with half a tank and it did same thing.

Kelly Barnett · Oct 17, 2013

It may be just me but what is the valve clearance in the engine. When cold the valves might have enough clearance to work pretty well. Then as the engine is warming up the valves grow and the clearance disappears holding the valves open slightly. This will give the engine a doggy symptom. Without having a dead spark issue like a coil getting hot I would think it would be mechanical with the valves. It isn"t a big deal to lift the hood and valve cover to check this. Maybe since the engine rebuild the valves are seating in a little farther then when the engine was first done. Just a thought.

mkirsch · Oct 17, 2013

I had a similar issue with a Cub Cadet 1250 that a neighbor gave me a couple years ago. It would start and run fine for a little while, then suddenly lose power and eventually die.

On that, it was a burned valve. Not saying yours is a burned valve, but it does sound valve-related.

Curt Cooke · Oct 17, 2013

Don't overlook the simple - better fuel?

super a runs bad when warm

pork

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gene bender

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Janicholson

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pork

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Phil Tibbetts

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Kelly Barnett

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Curt Cooke

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