Small Engines (Lawn Mowers, etc.): Onan 12.5 hp miss, valve clearance, speed adjustment

Question
Have a Toro Wheelhorse 212H with an Onan E125V in it.  Has new carb and mag. Have checked valve clearance and it seems to be OK, but at other than full throttle, it misses and backfires some.  At idle it will just backfire and shut off.  What else can I check?

Answer
Are there any leaks in the intake like old gaskets?  It sounds like the engine may be running lean.

Did you buy the carb from an Onan dealer or from Ebay?  Are there any ajustments on the carb other than the idle speed adjustment?

Let me know.
Eric