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What do you guys find to be the most common cause of oil smoke? I do not have it on steady run, but get a puff on acceleration and quite a bit on deceleration of the engine. This is a model 70 (K161) 7 hp that sat for 20 years, it starts and runs great and smooth. Prior to the first start, when I had the head off I was putting about a half inch of Seafoam on the top of the piston to try and make sure the rings were freed up. Maybe I need to continue with the Seafoam or does this sound more like valve guides?

I have been using the tractor almost every day, de-thatching, sweeping, spreading fertilizer so it is not sitting any longer.

Thanks for the Advise!

Dick Cupka

The first thing I would do is put a heavy load on the engine. Doing what you been doing with the 70 is a light load. I would vary the rpms from idle to wide open for 45 to 60 minutes while under a heavy load. . Them I would change the oil. I use Kohler brand straight 30 weight dino oil.

Is the engine using any oil?

How does the spark plug look?

The breather assembly may need remove and cleaned.

Question 7 of Kohler FAQs https://kohlerpower.com/en/engines/faqs deals with using additives in a Kohler engine. Kohler does not recommend using additives in their engines.

sea foam is an additive.

That's some good solid info Dale gave!

Any updates??

I once stopped the kohler in my neighbors lawn tractor from heavy smoking by running a healthy dose
of MMO through the gas tank.
I'm thinking it may have been a sticking piston ring (or somesuch).

The reason why the breather is critical, is simple:

When a piston engine is on power stroke, SOME pressure leaks past the rings into the crankcase.
Then the piston moves down into the crankcase, pressurizing it a bit. At bottom dead center, that cylinder pressure leaks back up, pushing a little oil through the rings. Remember... the piston fits tighter at the top, than at the bottom, because the top side's temperature is substantially higher than the bottom.

then the piston travels back UP on the exhaust stroke... but with no combustion pressure, the oil pushed up, is 'helped' by crankcase pressure, so it pushes it up far enough to lubricate the rings a bit... perhaps more than it should. At top center, the piston dwells for a short time, the valves change guard, and the piston starts it's trip back down, which creates a vacuum... that pulls oil up into the chamber.

And flatheads tend to develop slop in the valve stems, which vacuum and crankcase pressure tend to help push oil up into the intake valve, and that's why they get gunky and sticky and need MMO to keep 'em from binding up.

You will notice that it smokes more at high vacuum (meaning, high engine speed, but minimal load). When you put a heavier load on, the rings seal tighter, and the throttle is open farther, which means less oil propogation to the chamber. If the breather is clear, it's much less likely.