Farmall Cub

I would usually know this but having an off day. what would make a 71 10hp kohler exhaust smokle blue a few seconds after startup? I thought it would be the rings but this engine has high compression, always starts on the first crank. I suspected maybe valve seals but I cannot see them on the parts list I got, are there any valve seals or does it rely on the valves being upside down to keep the oil out of the cylinder... I just checked crankcase vauum and it is right on. It drinks a quart of oil every 3-4 hours of operation

I meant to add, I run quality 30W oil in it, and at full power when mowing it does not seem as bad as idling, allthough after mowing for 30 minutes it des smoke more than before.

If it is going thru a quart of oil every 3-4 hours, it is time for a rebuild. It will probably need to be bored .020 or .030 oversize to clean up the bore, since a Kohler will normally wear the cylinder more at the bottom of the stroke than at the top. Pistons and rings are available in .010, .020, and .030 oversizes. If the crankshaft needs to be turned, rods are available in standard size and .010 undersize. Just for info, a model 71 originally had a K161 7 hp engine. If it has a K241 10 hp, some one has replaced the engine.

Ditto on what Paul said

Sounds like rings for sure. Bill

It "could" run a long time that way, but the first time you forget to add oil (or its usage suddenly jumps) you may end up ruining the block when the rod punches a hole in it.

finally got the engine torn apart yesterday, poor piston had a meltdown once, it was missing a bit of material form the top and was 1/8 loose in the cylinder, everything else mint. the crank and rod looked better than new. monday morning it's off to the machine shop

How is your air cleaner filter? I noticed on most of the oil smoking engines I see score marks from dirt actually entering the engine thru the air filter, the carb and thru the intake valve into the cylinder, then the piston rings gall the dirt into the cylinder walls scoring or grooving it so the oil bypasses the rings. Thus the more we run it the worst it gets. I picked up recently another 12hp cadet engine that was replaced because of smoking. The PO stopped using it right away. I has one score mark on the cylinder wall. Again the cause is from not replacing the air filter. I have an awesome short block to rebuild. There's no noise or knock at the crank/rod bearing too. I needed a short block for another 12hp tractor that threw a rod thru the block. But I like to know the root cause before i repair anything.

With the two stroke dirtbike engines i see guys with boxes of used pistons because they didn't split the lower case and do the crank bearings and crank seals. What would cook the piston is an air leak at the crank and its 99.99% most to the time why the eat metal because there lean. On the two strokes. With the 4 strokes they eat metal when there is no oil to cool it and lube it. We must remember that with the 4 stroke engines the motor oil is also part of the cooling also. This is why the 30wt oil is recomended. Of course in thinking modern i tried the 10/40wt, a good quality 10/40wt and seen my 12hp cadet use oil. Then i did a test with a very cheap straight 30wt oil from walmart and she used no oil all summer. So what happens that it burns the 10/40wt motor oil. Its probably too thin and gets past the rings when the engine may run hotter do to the thinner oil. I think the thinner oil can also flow too fast to do any cooling so the engine may run a few degrees hotter too thus making the clearances expand more.

dhermesc wrote:It "could" run a long time that way, but the first time you forget to add oil (or its usage suddenly jumps) you may end up ruining the block when the rod punches a hole in it.

Your right i been collecting cadets with air conditioned blocks now. There's a big hole behind the starter/generator from the rods trying to get out of the block.

I just can't stress cleaning and changing out the air filter every year and check it during the mowing season too. If your running into the very high grass like almost were a brush hog is needed the machine gets covered with grass clippings and the air filter will
l catch the brunt of it too. I can only attest to what i'm doing and seeing when i run my cadets after all i'm learning too all the time.

this thing moved five acres under a 300 pound guy. I doubt it got any svc before I got it, the filter was horrible, I'm surprised it had oil left, although it did smoke less when I got it but took me a while to get it runing properly and by then it was smoking... maybe he used straight 50 oil