Small Engines (Lawn Mowers, etc.): Onan problems, needle valve, fuel pump

Question
I have a 1983 Case with an Onan engine. I have a problem with the mower not getting up to full rpm and it dies when mower is engaged under load. The carb and fuel pump was rebuilt last year and I double checked the float (brass) and the needle valve to check for sticking and they are fine. It appears that it is spitting oil into the air cleaner assembly. Any suggestions would be helpful.

thanks,
Tim in Michigan

Answer
With the age of your engine, the oil in the breather sounds bad, like worn out rings, for it to die under a load, it could be ignition, or compression/valve related, and adjusting the valves would possibly give you some more time.
  See if you can find a tag on the engine with the model number
so I know which engine you have,

Thanks