The next test should he a cylinder leakdown check. Pull all the spark plugs, get each cylinder in the firing order at top dead center with both valves closed, and put air pressure into the cylinder through the spark plug holes. Listen for leakage at the carburetor, tailpipe, and adjacent cylinders to find out where the pressure is going. Lock the crankshaft with vise grips clamped onto the flywheel to keep the air pressure from spinning the engine in case you miss TDC by a little.
Jerry
