51 A Won't Start

I have a 1951 A that I put new rings in last fall and had the head re-done. I put it on the dyno to seat the rings a bit. While it was running it would run ruff and loose power occasionally but came out of it. Thought nothing of it and took it home. Hauled the last of the corn harvest to town with it and ran fine. A few days later disced about 6 acres with it and it started running ruff and backfiring through the carburetor. Thought it was an electrical issue, replace some parts and it seemed to solve the problem slightly but never really went away. Finished my field and put it away. A few days later drove it from the shed to the shop and it ran terrible for 30 minutes then died. During that time it backfired through the carb and actually wedged the choke disc shut inside the carb so the lever would not move it. I rolled it into the shop and it sat for the winter. I have been trying to get it started this spring and get nothing. A small puff of white smoke is the most I get. I have checked and Re Checked the basics: I have good spark, I am in time, carb is spotless and getting fuel. Choke on or off has no effect, throttle position has no effect. One unusual thing is after cranking for several minutes. If I open the petcocks, #1 cylinder is hardly any fuel in it but fuel comes gushing out #2 petcock. I am not sure what else to look for. This tractor is my planting tractor to boot and pulling a 494A with this is more fun than the 4230. Any help would be appreciated. Thanks.

Get a set of fresh hot spark plugs. Your are not working well under compression.

Have '51 AR I kept having similar problems with and it was always the condenser. Been going fine for a couple of years now so I must have finally got a good one.

Sticking valve is the only way they blow back thru the carburetor with that much power.

Rocker arm oiling should have been checked for in the first ten minutes with the valve cover off and not a come and go kind of deal usually. But the rough running from lack of oil there certainly will have spurts that seem to go away. Don't forget to check for bent pushrods because of a stuck valve. A straight one will spin easily between thumb and finger once it has zero pressure on it from proper .020 clearance adjustment.

Damage is usually not bad enough to require taking the head back off. Just restoring good oil flow to only exhaust is enough. They usually recover fully and cause zero issues from then on. But to help speed the process, do put some oil on all valve stems occasionally until it runs smoothly for a half hour straight. Put the valve cover back on it and run it like you just stole it.

A drop a second is usually all they do. If you have three seconds of nothing, take the tube off the head and shoot it full of canned brake cleaner followed by shop air, repeat until strong shop air jets come out of both oiling holes.

He says valves are only thing that causes to backfire though carb...wrong... I'm going to say you have either a blown intake manifold gasket or your manifold is cracked inside and if so it will blow exhaust through carb and also create lean mixture which will also backfire. This would explain one wet and one dry plug also.

Remember... one leg of Mom's Panty Hose over the air inlet stack (while not being used or run) will prevent much trouble from Mud Dauber nests above the air cleaner ( in the Dog Leg)..