The unit under test is a Troy-Bilt chipper made in the late 80's. Engine is an 8 HP Briggs. It appears to have very low hours. The engine starts easily, runs well for about 20 minutes, then begins to drop RPM and return to normal operation. Loading appears to have no effect. Eventually the engine will come to a halt. The engine will start again, like a hit or miss engine, coughing puffs of smoke, and ramp up to full operational speed.
So far: Fresh gas with a healthy dose of Sea Foam. Plug is new, dry, and a gray-cream color, no carbon. New synthetic oil in the crankcase.
Any suggestions?
Kevin Gallimore