Re: Powerhead Advice

[Don]

OK, so this is not your engine, and you probably don’t know any history on it. But, ask your friend anyway.
The fuel pump may not be working just because of all the strange crankcase pulses while sneezing/coughing. But, it is more likely that that there is an airleak/fuel restriction somewhere. And again, this may be an issue of a low fuel tank height due to the test tank.
Ask your friend how the engine ran the last time he used it. You said you had the carb apart, was it gummed up inside?
Are you SURE the throttle plate is closing/not jammed/synced properly? These engines are cold blooded on their best day. Have you checked compression and spark? This engine uses the beloved low tension ignition, perhaps a weak ignition is causing all the fuss, have you tried new plugs, even though the ones you are using might be "new"?