The crankcase breather is a flapper valve that works
with movement of the piston. It opens/closes to prevent
a pressure from building inside the crankcase. Tecumseh
single-cylinder engines have NO SEAL on the governor
shaft, and they are "subject to drip" from that place.
This hurts nothing (except the garage floor), and is
more "aggravation" than anything else. If the oil leak
"seems excessive" and the mower is within the warranty
period still...I'd plead my case to where I bought the
mower. The "ONLY FIX" is to replace the engine, and it
may not solve the problem. Feel free to e-mail me if you'd
like to discuss this further.
Walbroman