782 Crankcase Breather Question

[Cubpwr1811]

My 782 with the KT 17 Series II engine always seems to be pushing oil out somewhere on the engine as if the crankcase is pressurized and not breathing properly. I replaced the crankcase breather with the newer style valve sometime in 2016 so it's still pretty new, but even when new it pushed some oil out in places.

Last weekend I just degreased and cleaned the entire engine to get it ready for the mowing season. So last night, I mowed for a couple of hours and when I got done I lifted the hood and found my engine just covered in oil. I could see where it had pushed out oil around the governor shaft, from under the points cover, up through the breather tube and out from under the dome on the air cleaner, and even around the threads on the oil fill neck.

Do I just have a bad crankcase breather valve again? Or could there be something else going on? I lost so much oil last night that the oil on the dipstick was just barely in the safe zone after mowing, but was right on the full line before mowing. I have never lost that much oil that fast before. I did have a leaking rear main seal behind the PTO clutch last season that I replaced over the winter, so I don't know if that was easing some of the pressure from blowing oil out everywhere else I mentioned and now that that release is gone it's blowing out everywhere else or what. Any help/thoughts is/are appreciated?!?

[olds45512]

It's possible the breather is plugged, it's also possible that the engine is getting wore out and has a bunch of blow by which would put more pressure in the crank case than the breather could handle. Does the tractor smoke?

[Cubpwr1811]

No it doesn't smoke, in fact I had this engine completely rebuilt about 200 hours ago by my local cub dealer so I know it isn't worn out. I'll have to check my breather out and see if anything is plugged.

[ol'George]

"engine completely rebuilt about 200 hours"
So exactly what was done? to some, complete rebuilt is a seal or two maybe a gasket and spark plugs.
A complete rebuild is oversize pistons/rings, valves/seats ground, or replaced, crank turned new seals/gaskets and ignition components among other things.
I'd clean it up and run a compression check just to see where you are at.

It sounds like you have something seriously wrong to blow that much oil everywhere,---- or you have a blown crank seal and the fan is blowing it about.
The crankcase is not pressurized normally.
As the crank turns it pushes the pistons out into the cylinders simultaneously,
then pulls them back simultaneously, alternating between vacuum and pressure.
In real life you wind up with a little pressure in a worn engine, a new engine has a bit of vacuum, maybe.
It is covered in the service manual and measured with a manometer
Make sure your breather valve is functioning/installed properly and the little orange neoprene sleeve is installed properly over the stud.

Some shops don't know which end of a spark plug screws into the heads.
others are more educated.
Let us know what you find.

[john hall]

You do have all the screws in the point cover, right? It seems I cranked one of those once with the point cover off and oil went everywhere. It's been a few years, just tossing it out there.

[darkminion_17]

I tough of tat, maybe no gasket in there.