john_bud said:
Did you flush out the old gas (or has it been running for a while?).
It may also be bad wires, a short in the distributor, bad cap or rotor or even water under the cap. Lot's of little things that crop up when you bring one back from the dead. Do you have a filter on the fuel before the carb? Can be lots of "stuff" in there.
jb
Just to add to what jb said, moisture or bad wires are typical reasons for missing, especially under load. I'd use a hair dryer to dry out the inside of the distributor really well. I'd also look at the wires. I think most of these old tractors used stranded wire plug wire and it may deteriorating and the spark jumping from wire to wire or on dirt residue on the surface. Running the tractor in the dark and looking for sparks jumping is what I normally do.
Any residue that is on the wires or plugs can collect moisture and jump a spark. If you are sure that the plugs are not fouling out, then look for moisture or contamination. Also look for any loose ignition wires that could be making intermittent contact due to vibration. Pull each plug wire and coil wire out of the distributor cap and look for "issues."
If plugs are fouling out, you can sometimes jump the spark to the plug electrode and the plug will fire. You can build a jumping jig with a piece of cardboard, or if you are really brave, you can pull the plug wire and hold it in your hand. Be ready for a few surprises
if you don't do this right.
Finally, if the points are bad, normally the tractor won't even try to fire off. If it fires off and misses randomly, it's probably not the points, but you can never go wrong by making sure the point gap is set properly and the contacts are clean. I used to rotate the engine until the points are closed, then turn on the ignition and open the points with a screwdriver to get a spark. This will tell you if the points will work under normal operation.
I'd say to check the condenser, but they don't go bad very often. They are always included in a tuneup set, but rarely are they the cause of ignition problems.
