HH100 smoke out breather

Andy, if you have a service manual, check out the section showing the use of a Manometer for a diagnosis. An HH100 that produces lots of blow by, it is almost always caused by worn rings. You may find the cylinder worn beyond the acceptable limits, maybe not. The piston will also be burned at the top land, enough to see part of the top compression ring, toward the valves. The top land is smaller than the rest of the piston skirt by design.
I think you will want to locate a new head gasket, then pull the head to check the marking on the piston and check the part of the cylinder you can see for size and condition. Then start looking for new parts that might be available. Tecumseh used to offer a .040" oversize piston and rings, but probably all sizes are difficult, if not impossible to find now.
You might be able to locate another Deere specific block to rebuild if yours is way out of limits, or oversize parts can't be found.

Unless the valves/valve guides are really worn egg shaped (+.005-.010), don't worry too much about them causing a lot of oil usage. Oil drawn past severely worn valve guides will show at the exhaust pipe.

How do you use this tractor? If it's your one and only weekly mowing machine, keep up the "topping off" of oil as you decide how to solve the engine problem that best suits your time and economics. Let us know how it's going.

tommyhawk

Yes, Bill. BTW, Kohler "K" series have less valve stem to valve guide clearance than Tecumseh HH100 to start with. With a properly functioning crankcase breather, including oil drainage back to the sump, there is a minimal amount of oil in the valve stem galley. My reasoning is with excessive c/c pressure (blow-by) some oil is pushed/sucked past the stems into the combustion chamber to be burned or exit as unburned oil in the exhaust stream making a little smoke. You would likely see the smoke when the engine is first started, not so much when running. The exhaust pipe would show more soot than raw oil. The accuracy of the valve guide to stem clearance is important to assure the valves seat properly every time as they close.

The point I wanted to make is moderate to excessive oil consumption is more likely caused by a bad oil control ring than worn valve guides. If the oil control ring is stuck, worn, or lost its tension and the compression rings and cylinder wall are still in good condition, smoke and oil consumption can occur in an engine that otherwise "runs strong".

One exception I have run into was on one of the early model Tecumseh OHV engines in a Craftsman rider. The guides were worn at least .020" egg shaped. That thing drank oil but ran very well. The rocker arm geometry was horrendous! Replacing the guides solved the problem at least till the rest of the mower junked out.

tommyhawk