OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk My Briggs 11.5HP rebuild

I suggest you remove the rings and clean the grooves, Aldo - there could be some rubble in there. Be careful not to remove any metal from the piston, of course. You might measure the ring gaps, with each ring in turn pushed down about 1 cm from the top of the bore. Use the top of the piston to push them down square to the bore. If they are any more than halfway between new and maximum allowable gap, it makes sense to replace them while the engine is dismantled. Incidentally that tiny score on the side of the piston is of no consequence in a 4 stroke. You do need to linish across it with some fine emery or wet and dry though, in case the ends or edges of the score are raised up.

I've seen crankpins that looked like yours, after your cleanup, that seemed to work quite satisfactorily. It doesn't look excessively rough. So far as the divot out of the crankpin is concerned, it depends where it is. The most sensitive spot is near the highest part of the pin when it is on TDC, because that is where the maximum pressure is applied to the rod by the piston. In essence, I wouldn't be even inclined to try a divoted crankpin on a modern car engine, but on a splash-lubricated side valve engine with a maximum speed of 3,000 rpm and a compression ratio of 6 to 1, I'd try to re-use it myself, and be hopeful of success. I can recall a friend hearing a relative arrive in an ancient Ford 10 (1940s/50s side valve with splash lubrication and white metal cast into the rods, no bearing shells) and noticing that one big end was clattering horribly. My friend took out the rod and soldered up the big end with a plumber's iron using ordinary solder, then scraped it a bit and put it back together. By the time the relative had finished socialising, it was ready to go, and it apparently lasted for years. There's something to be said for low tech, low stress engines. Edit: By the way, crankpins are not usually hardened. I can recall when Austin Healey made a racing version of the first model Austin Healey 100 in the early 1950s (the racing model was called 100S), one of the engine modifications to make it suitable for the Le Mans 24 hour race, was to nitride the crankshaft. To wander even further off topic, the 100S engine also had a different cylinder head from the 100 model - a conventional port design instead of the extraordinary, perhaps even insane, design of the standard head, which was taken straight from the Austin A90.

Please be sure there is no aluminium deposited on the bore, that would be unlikely to work well. You can easily polish deposits off the bore the same way you cleaned up the crankpin.

I can understand the problem with the old lady keeping the place going after her husband passes on, and not doing the necessary mechanical maintenance. I can recall an old guy buying a tiny Japanese car new, then dying a couple of years later. His widow kept driving it, and putting petrol in it. After 3 or 4 years it finally seized. Still hadn't had its 1,500 km free service, let alone had anyone look at the dipstick.