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K301 leaking oil

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danderson

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Doug Anderson
Have my buddy’s 129 here. Looks like it’s leaking oil out the flywheel side seal. I know the seal could be and probably is bad. My question is I popped the dipstick out a little while it was running. Got a lot of pressure out of the hole. Could there be enough crankcase pressure from cylinder issues to force oil past the seal?
 
My question is I popped the dipstick out a little while it was running. Got a lot of pressure out of the hole.
Doug - Leave the dipstick alone when engine is running, not unusual to get pulsations (and sprayed out oil) from it if removed, as you have found already. There is some theory about how the breather works and vent sizes etc that someone else would better explain then I. I'm sure someone else will chime in.
 
Doug - I did not mean something was wrong with the breather. There is a reason why the air pulsates out the dipstick with engine running and it's quite normal, is what I meant. The reason it pulsates has to do with the normal operation of the breather along with piston travel, venting etc. I'm sure someone else can explain the theory of why better than I.

My guess is that pulsation is not why the oil is leaking from the seal, probably just a dried out/worn out/cracked seal is why it's leaking.
 
I made a Manometer to check Crankcase vacuum. Its just a U-shaped clear tube fastened to a board with one end connected to the dipstick or other connection to the crankcase. (Above the oil, of course.) There are directions in the old K-series manual, at least there is in my copy.

The reason there is a pulsing in the crankcase is the piston. When it goes up in the cylinder it creates a vacuum and when it comes down it creates a pressure. The idea of the crankcase breather (reed valve) is to maintain a small amount of vacuum in the crankcase so oil won't be forced out through the seals, gaskets and governor bushing every time the piston comes down the cylinder.

If you make your own manometer, put some kind of shutoff valve in the line to the engine. I made mine with 1/4" clear tubing from a pressure washer soap injector, so I just used a 1/4" fuel shutoff valve.

You need the shutoff. On single cylinder engines, when you hit the starter, the first time the piston goes up in the cylinder it can suck all the water in a 1/4" hose into the engine. After it starts, the change in pressure is happening so fast they almost cancel each other out. Just connect everything, make sure the shutoff is closed, start the engine, open the valve and read the difference in height of the water with a yard stick from one side of the tube to the other.

If you plan on keeping water in the manometer, its a good idea to put a little anti-freeze in it. it also makes it easier to read.
 
49335D46-D208-4389-9C41-DCA0946F88C4.jpeg

Probably why it was leaking
 
So in the seal picture: the seal was blown right out of the casting because: the breather wasn't working proper? Because the ID of the seal seized to the shaft ripped and spun out of the casting bore?
 
I pushed it back into the bore and it was quite loose. Someone was in this engine before. Has a .20 over piston and the balance gears are gone. Maybe reused old seal? Don’t know. Took the breather apart and it was fine. New seal fit nice and tight. Added a little locktiie just to be sure.
 
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