On Sun, 8 Mar 2009 16:50:52 -0700 (PDT), oldjag
wrote:



Sounds like it may be to lean to accept the load. As others have
noted, see what the throttle is doing when it won't accept the load.
It's probably opening up to no avail. If the jets are clean and you
have good fuel flow, make sure the float level is correct if this is a
float type carb., otherwise check for any air leaks that might be
leaning it out. It does not take much of an air leak on an engine
this small to give a lean condition.

A leak wouldn't surprise me. The carb mounts outside a plastic shroud
that surrounds the engine, and as best as I can tell, the shoud is
sandwiched between the carb and engine. When I removed the carb, the
gasket between the carb and shroud looked OK, but I have no idea
what's going on at the other interface.

As these carbs don't usually
have an accelerator pump, the carb needs to be a tiny bit net rich to
accept a load increase when the governer pops the throttle open.

Right, no accelerator pump.

Weak
ignition can also behave somewhat like a lean condition, as a lean
mixture takes more voltage to fire as does increased cylinder pressure
which occurs when the load is increased. Make sure you have a healthy
spark, ie it can jump at least 3/8".

Probably wise to replace the plug as well then, but that means a trip
to town.

--
Ned Simmons