20 HP Kohler
 

I have an interesting issue that just happened for the second time. The oil fill cap has come loose and blown off while mowing and blows oil everywhere. It happened for the first time last summer so I bought a new cap figuring the rubber gasket was getting worn from a few summers of mowing. Then it just happened a couple days ago only after about a year. Is this common? Now I'm trying to figure out how to tether it or make something so that it can't turn by itself and blow out. Of course I never was able to find the caps that blew off.

First ...welcome to OCC... :Welcome2:

20HP doesn't tell us much. How about a specific Model number (ie: M-20, CH-20, etc).

Too much crankcase pressure...

And what caused it? Possibly a crankcase breather malfunction? Excessive blow-by? :bigthink:

All the above

Thanks, I'm new here if you couldn't tell. It's a Kohler command v twin. Only 5 or 6 years old. I assume it's a CH.

But why? And what is the fix?

Bad or plugged Crankcase Breather. Now that we know you have a CH-20, we can look it up.

I'd say you didn't put the cap on tight.....

It only goes on til it stops.

Well.... yeah. But it's a screw on cap is it not? Threaded cap. Not a 1/4 turn cap correct? So, you screw it on until it stops, then make it tight. Just like putting a lid on a bottle of soda pop. Even in the crankcase pressured up too much, it would blow the seals out before it blew that cap off.... unless you didn't put it on tight and it unscrewed then vibrated loose until it popped off. That or you didn't reinstall it at all, and took off not knowing it, only later to discover it missing. Believe me, if you had a crankcase pressure issue, it would be doing a lot more bad stuff besides randomly losing the oil fill cap 1 time a year. Like I said..... I bet you either didn't reinstall it after topping off the oil, or it came loose. Happened to me before, so don't think I'm making fun. It happens.

Or the first guy stripped the threads with his 48" pipe wrench:bigthink:

:bigeyes: :biggrin2: :ExtremeFunny:

No, it's a 1/4 turn cap.

If it is a 1/4 turn cap then your 20 horse command is a late model command. The CH 20 originals have a screw on cap that you can tighten down. I have an original ch20s in a 2084 and never had your problem.

It turns a quarter turn, or it's a quarter turn cap?

A quarter turn cap would have two tangs on it. If it has threads, it's a threaded cap.... that apparently turns a quarter turn to tighten. Two very different things.

If it is a true 1/4 turn cap, I want the model number of the engine, because I've not seen one with a 1/4 turn cap.

A picture can tell a thousand words or posts. :biggrin2:

Here is a 1/4 turn cap. CH22, this one is in my 1864/2264
:beerchug:

There we go. :beerchug:


To be fair, that is a new motor..... not a Cub Cadet spec''d motor. And a 22hp, not 20. :BlahBlah:

When you lost the original one last summer and replaced it, could the dealer accidentally have sold you the wrong style? A 1/4 turn instead of a screw on? Or, vice/versa. Or perhaps the part box/bag was mislabeled?

Things happen.

Oh boy, picky picky...
This is in a 2185, they are suppose to have an "O" ring on it....

Yep, it's a 1/4 turn cap, just like the ones pictured and it does have an O ring on it and I did turn it all the way and I do check it every time before mowing when I check the oil because it came off before. This is not my first rodeo. I've been mowing with a rider for over 40 years and have never seen anything like this happen before. My best guess is that after a year or so the O ring loses it's elasticity and becomes loose allowing the cap to turn enough to get blown off. Just wondered if anyone else has seen this happen. When I replaced it I got the exact part number listed in the manual after borrowing the one off my neighbor so I could finish mowing. I have since installed an oil cap detainment system (ty-rap) to keep the cap from turning.

It is a Cub spec. Perhaps someone changed the valve cover. 20 & 22 would use the same valve covers.

Does it ever fall off/unscrew it's self, Lew?

I can verify that Cub did at one point or another spec an engine like that. The Command I have in my 2284 came from another Cub and has the same setup as in the pic you posted, Sam :beerchug:

No it does not unscrew, I just got done cutting the grass, but I still have to fiddle with the carb more. Another project.