OutdoorKing Repair Forum Forums Restoring, Customising and Modifying Tech Talk Kirby H4-4A engine rebuild

This next bit is on the bottom end stuff.

After drilling a couple of small holes in the oil seal and then picking it out, the small circlip beneath can be removed. This then frees the rear half of the crankcase for removal.

The governor is an interesting device. It is a shaft mounted device close to and gear driven from the crankshaft. When the little weights deploy as engine speed increases, they push on a disc then on an internal lever that is attached through the crankcase to the spring loaded external lever and thence to the throttle butterfly via a bent rod. Clever and a little more sophisticated than the air-driven Briggs & Stratton governors. The connection passing through the crankcase is suitably sealed against oil leakage.

The internals are quite standard with crank, camshaft and valve lifters in the usual places.

More photos are attached - taken after cleaning 30 years of crap out of the crankcase.



Bottom bearing, crankshaft and circlip prior to installing new oil seal.



Governor with top disc removed showing the weights deployed.



Reassembled governor.



Valve lifters and governor lever. I've still got a bit more paint to remove off the air vanes.



Bottom end showing oil splasher. Apparently, some of the US models had a small oil pump and pressure lubricated bottom end.



New bearing in outer half of crankcase. Now so clean you could drink your soup out of it

I have to go out now, but I'll pick this up later,
Chris