bar oil leaks a lot of oil only when saw is running

[GIBSAW]

I have an older Stihl 011 ATV chainsaw. I recently removed the plastic cover, blade & chain to clean it, something I've done many times in the past.
This time, after I put everything back and started it up. A short time later, I noticed that a lot of chain oil was coming out from the bottom part of the cover. What could be causing this?

 

[Bob Hedgecutter]

At a guess- if you used compressed air and managed to direct a blast down down through the hole in the bar pad the oil comes out of- you may have torn the diaphragm in the impulse pump, or damaged the spring under the diaphragm, or blown the foam filter off the pick up side.

 

[GIBSAW]

At a guess- if you used compressed air and managed to direct a blast down down through the hole in the bar pad the oil comes out of- you may have torn the diaphragm in the impulse pump, or damaged the spring under the diaphragm, or blown the foam filter off the pick up side.

I didn't use compressed air for cleaning. However, is your description of "the diaphragm in the impulse pump, or damaged the spring under the diaphragm, or blown the foam filter off the pick up side" referring to the parts of the chain oil pump and its filter??

 

[Bob Hedgecutter]

I didn't use compressed air for cleaning. However, is your description of "the diaphragm in the impulse pump, or damaged the spring under the diaphragm, or blown the foam filter off the pick up side" referring to the parts of the chain oil pump and its filter??

Yes- the pump is driven by crankcase impulse and has a diaphragm in it just like the carb has one, on the back of the pump is a solid tube pick up with a foam filter. There are also two gaskets in the pump.
Pretty sure the gaskets and filter can still be bought- but the diaphragm is no longer available.