I would first check the Injector Pump Plungers (easy to do, just remove the cover plate) as mentioned before. You could also have a Valve sticking. Probably wouldn't be a bad idea to remove the valve cover and check for sticky valves. Give each valve stem a few drops of oil while you're at it too.
'46 Willys CJ2A Farm Jeep, '49 International KB-7, '31 Allis Chalmers U, Cushman Scooter(s)
Antique garden tractors & outboard motors
Other rusty old junk comes & goes without warning.
The 2 most useful tools to have in your shop are a Crystal Ball and a Magic Wand