Briggs & Stratton OHV Plastic Engine No Compression

[RevB]

I don’t even know of a machinist in our area that will grind valves. When you factor in your time back and forth, and paying labor cost, it would be on the expensive side. Even new valves need to be lapped in to the old seats.

Automotive repair or engine rebuilder....most straight machinists don't.

 

[GearHead36]

Lapping does not increase compression.

I disagree. I used to race karts with 5 HP Briggs flathead engines. I ran open class, and the engines peaked out around 6000 RPM. At the end of a race, compression would be noticeably down from the start. I would have to basically do a valve job after every race. I'd remove the head and valves. I'd decarbon the valves by spinning them in a drill press, and cleaning up with steel wool. Then lap the valves. I'd use 3 compounds. Course, fine, and polish. Re-set the valve clearances, then reassemble. Compression went way up after doing this.

 

[RevB]

I disagree. I used to race karts with 5 HP Briggs flathead engines. I ran open class, and the engines peaked out around 6000 RPM. At the end of a race, compression would be noticeably down from the start. I would have to basically do a valve job after every race. I'd remove the head and valves. I'd decarbon the valves by spinning them in a drill press, and cleaning up with steel wool. Then lap the valves. I'd use 3 compounds. Course, fine, and polish. Re-set the valve clearances, then reassemble. Compression went way up after doing t

I disagree. I used to race karts with 5 HP Briggs flathead engines. I ran open class, and the engines peaked out around 6000 RPM. At the end of a race, compression would be noticeably down from the start. I would have to basically do a valve job after every race. I'd remove the head and valves. I'd decarbon the valves by spinning them in a drill press, and cleaning up with steel wool. Then lap the valves. I'd use 3 compounds. Course, fine, and polish. Re-set the valve clearances, then reassemble. Compression went way up after doing this.

After every race. A complete valve job. Decarbon. Ohhh Kay.