Stihl 011 AVT bar oil leak

[GIBSAW]

Hello-
A few weeks ago, I removed the plastic housing cover of the clutch & where chain goes around the sprocket, etc., I removed the chain and the bar & carefully cleaned out the debris top to bottom, something I have done on numerous occasions. Put it all back together, etc.
After it had been sitting for a week, I picked the saw up and noticed there was a good amount of bar oil that had leaked out from the bottom area where the bar disappears into the machine.
Never had this issue before, but since it's some 30+ yrs old, maybe a gasket or seal needs replacing....?
Any ideas as to what might cause this?

 

[Bob Hedgecutter]

Can you clean it up and determine exactly where the oil is leaking from?
009, 011, 012 all leak oil and at the age they are now- are well known for it.
Hard to stop an one from leaking bar oil when the tank vent is a cotter pin in a hole. Make sure the hose has not separated from the pump
Other than that, drain the fluids from the saw and store it, or you WILL have a puddle of oil.

Genuine pump diaphragms are no longer available, but there are rebuild kits and high flow kits available for the oil pump to be rebuilt- IF that is the issue.

 

[GIBSAW]

Having cleaned all the bar oil off the bottom of the saw casing, I let it set for a week. I then pick it up & looked to
discover: no leaking bar oil. This means that it only leaked oil after I used the saw, and maybe it was leaking when
the saw was being used...?
But I still have a question.
I knew the gas tank is vented and I can see the hose connection. But until now,
I didn't know the oil tank was also vented.
Where is the location of the 'cotter pin in a hole' and the (vent) hose for the oil tank?
The mystery deepens.

 

[Bob Hedgecutter]

The oil tank vent on these is located on the bar mount pad- directly behind the bar stud.
It is not a "vent" as such, but a simple drilling through the side of the case, with a split pin/cotter pin installed in that drilling- which allows air to enter the tank to replace the oil that has departed and somewhat negates the oil seeping out.