oil blown out

[fdsinozich 1]

I recently purchased a 1974 C-120 auto. Five minutes into my first mowing, oil blew from the breather tube all over the front of the engine. I cleaned it up and used it again today with no oil blown out.

Do I have anything to worry about?

Thanks,

Frank

[rmaynard 14,934]

There should be a negative pressure in the crankcase when running. Bad rings or a stuck ring could cause blow-by and thereby cause pressure to build up in the crankcase. The ring could have unstuck again, and the problem went away.

Also, could you have added too much oil?

[Horse-Drawn 1]

I've seen that happen when the inside of the muffler is loose or collapsed. It causes a restriction that will create positive pressure in the crankcase & oil blowing from the breather. It can be tricky to catch because driving over a bump can jar the restriction out of the way with barely any detectable tone difference from the muffler. Heck, I've even seen that caused by someone getting too creative with their exhaust routing and having too many 90 degree elbows. Each one reduces cfm potential and will increase back pressure on the engine. Cheaply made elbows get very narrow causing the same result. 5-10" of vacuum is normal range & it doesn't take much to counter it via exhaust restrictions, stuck rings, valve guides, or bad case gaskets. :thumbs:

[fdsinozich 1]

Thanks, guys.

The oil level was correct. I added one ounce of Seafoam when I first got it, perhaps it freed what ever was stuck. It has the oem exhaust. Maybe I got lucky and it won't happen again.

Thanks again, I really appreciate the input.

Frank

[fdsinozich 1]

It did it again today, only happens at full throttle.

I'll look some more.

[sorekiwi 761]

The Kohler manual has a section on how to check crankcase pressure.

I had a K181 that ran great, and didnt smoke at all. It would putt around all day dragging a cart, but if I tried to mow with it there was oil everywhere.

After pulling the breather apart a couple of times I finally checked for crankcase vacuum and found that it was indeed pressurising the crankcase under load. The subsequant teardown found a worn bore and rings. I still dont know why that motor didnt smoke though.

[Martin 2,130]

try pulling the breather assembly out and giving it a really good clean. new filters are available so if its not usable replace the filter(s) in the assembly i read in the manual that some have two screens. think it was k181 new style but not sure off the top of my head. anyway if the filter is really bad install a new one and see if that makes a difference. im not saying what others said in this post isnt something to worry about, they all have valid points, but do the simple stuff first. there is alot of air in that crankcase that needs to go somewhere and if the breather reed and filter and oil drain in the breather body arent working as they should then its going to puke the built up pressure and oil out that vent eventually. follow the manual, make sure its all clean and the reed is flat against the back body vents (it needs to be clean and flat against those holes to be able to do its job) and the oil drain on the breather back plate is down. see if that solves the problem. not saying its the answer to your problem but that crankcase needs to breathe and the breather can only perform well if its clean.

martin

[B-8074 19]

I would do the breather for sure since you've been spitting oil from it. After that I would run it without the muffler or a different one. Like mentioned before, if you have any loose material in there it may only show up at high RPM's.

[fdsinozich 1]

Thanks, Guys, I'm going to clean the breather this weekend. If no luck there, then I'll try mowing without the muffler. I can't find any markings on the engine to identify it, any suggestions on where to look?

Thanks,

Frank

Roanoke, VA

[Horse-Drawn 1]

C-120... That would be a 12hp, K301, right?

[fdsinozich 1]

I don't know, the guy I bought it from told me it was Tecumseh 12 HP. I don't see any markings or I just don't know where to look.

Thanks,

Frank

Roanoke, VA

[Horse-Drawn 1]

It's possible...

They had both.

Kohler K301S-47421D

or

Tecumseh HH120-120180D

[fdsinozich 1]

Jay,

If it is the Tacumseh, does that change your recommendations?

Thanks,

Frank

[sorekiwi 761]

If you have a Kohler then it will look pretty similar to this:

Note the word "KOHLER" is stamped into the top of the blower housing.

[Horse-Drawn 1]

In short... No.

If it's the HH120, I'd say it more likely to be a bore/ring issue.

But...They are basically the same engine. Same design, same theory of operation, same needs to function properly. Their differences lie in the patents on cam grind, piston design, head design, shroud / cooling design, and in part quality. Kohlers have a rep of handling more stress, more heat, more tolerance to lack of regular maintenance. Mainly, in my opinion, due to superior design and superior part quality. Don't take that as a slap to all the great running Techs out there, but in unmodified form, most people(users & mechanics) will agree the Kohler is the more dependable product.

All the advice members have given would apply to either engine. You just have to eliminate the possibilities one at a time.

Hope I helped & not complicated :thumbs:

[Horse-Drawn 1]

This is not something I'd recommend doing, but if you're not wanting to sink cash into the motor right now(if needed)...

I've seen guys remove their dipsticks & install an automotive valve cover filtered breather on top of the top of the dipstick tube. It allows the positive pressure to vent faster & you're less likely to puke oil from the original breather. It doesn't fix the cause, just the mess temporarily.

I wouldn't do it to one of my engines, but it can be done.

[fdsinozich 1]

It is a challenge, but I will tackle it this weekend. I'll let you know what happens.

Frank