Kohler magnum 18 excessive blowby

Hey y’all. Recently I’ve been ripping my mower around and I’ve had a couple smoky instances. I was riding down the road and I had it full throttle for a few seconds and then it just poured smoke out of the exhaust and died. My heart sank as I thought it had blown up. I cut it off and tried to start it again, started up. No problems until a few day later. I was mudding it and I noticed just a little bit of smoke from the exhaust so when I got home I pulled the air filter to find it damp with oil. The second time I think was just excess blowby through crankcase vent into the air filter, could be solved with oil catch can. My real worry is about the first time where it poured smoke. Anyone got any ideas?

Could be a number of things. A couple I can think of, clogged pcv. Found where that tube meets the valve cover. A second thing could be worn rings. Letting some compression leak into the block and that pressure has got to go somewhere. Just could be over revving it. I'm sure some others will pitch in ideas.

My theory is also clogged pcv. Take it off and clean it good with some degreaser or gasoline or diesel. It’s a seal and over time as it opens and closes it wears. I had to change mine out and it made a world of difference. As far as the oil goes, maybe some got sucked into the carb? I wouldn’t worry as long as there isn’t a pattern of smoke at start up, then try a cold compression test. Hope that’s helpful.

You think the clogged pvc could have caused it to puff smoke and die? Not venting so it builds up crankcase pressure and pushes oil past the rings? I was just in there replacing valve cover gaskets and it all looked fine. Less than 3 hours on it since. The valve you’re referring to is the small reed valve in the valve cover, right? I might hook up a temporary water bottle catch can to see what I collect before I buy a catch can. Btw last compression test it ran 90 on my harbor freight tester which reads low.

90psi on a mower engine isn't bad, remember most mower engines have some sort of compression release.  One of my engines gets only 65 but runs fine. The low range on the tester is for like an auto engine.  I have an onan stored out in my shed that has excessive blow-by due to bad head gaskets.  Just trying to throw some ideas out there for you.  Easy check for blown head gasket (not a sure fire way), after running it.  When you shut it off, pull out your oil dipstick and see if some foggy smoke comes up.  Last thing I can think of, possibly your needle and seat on the carb is letting fuel leak when not running?  Allowing fuel to leak into engine.  Maybe check oil level and if oil has gas in it?  I had a generator with that issue, started blowing oil out the exhaust though.

No I know 90 is good, I’m saying that’s it’s actually more than that because my tester reads low. I was having a small issue with the needle and seat, but I fixed it and changed the oil. Maybe doing it again. I’m thinking the combination of old engine, high revs, and bouncing around is probably the problem.

Yeah the reed valve is the PCV. I wouldn’t buy a catch can, the breathers aren’t terribly expensive, figure 30 or so for the kohler by my google search. My vanguard was 40 and that included the related gaskets. Check your head gaskets though, they might be slightly blown.

Alright, I’ll take a look at the head gaskets, but it doesn’t really run bad, just those incidents with the smoke.

Educate this old man please. Engines of my era (early stone age) didn’t have a valve, just a hole in the cover. So, why do we need a PCV now? Just for California or what?

Probably to keep the dust and other crap from getting into the engine. A big push for cleaner oil was made about the early 90s in small engines but maybe it came sooner and I’m wrong.