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. 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. 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".

It also needs to be a tiny bit net rich to make sure that the piston
crown remains in one piece. Air cooled engines and lean running, not
a good combination.

Change the plug - it's a cheap problem point to eliminate.

Might need to run a video camera watching the throttle as you load
it up - Paint the linkage for good contrast. It could open fully as
suspected, but once the computer sees that the engine isn't responding
to the throtle call and working harder after a second or two, it slams
to Off and does a load dump. You would need to review the video to
see it.

Rig your own variable load bank - get a Contractors Work Light
string with ten lamps, and then you can screw in the lamps one at a
time (with gloves on!) to vary the load.

-- Bruce --