Mini roto-tiller - loses power (stalls under a load)?

I have a Homelite mini roto-tiller that just wants to stall when it is put to work... any idea why? The spark plug looks "ok". I blew out the carb and air filter with compressed air. I serviced the clutch and worm gear box myself a while back and it worked good for a while. Now it just wants to stall when it is put to work. Could it be a carb setting? I don't have an operation manual, so I am reluctant to touch the settings on the carb.
Any ideas, suggestions or advice would be great! I could just take it to a mechanic, but this might warrant buying a new one... I'm not crazy about spending money on repairs if I can figure it out myself.
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