Don Tuite wrote in message . ..

On hot days, the O-300 in the 'Hawk tends to diesel on after you pull
the mixture. Opening the throttle a little makes it stop.

Don,

Sounds like you have a fuel leak into the manifold. Pulling the
mixture to cutoff should, well, cut off the fuel flow. This could be
something in your carb, or might be a leak in your primer system.
Either way, it shouldn't continue to run after you've cut off the fuel
supply. That's an indication of a problem in the fuel system.

John Galban=====N4BQ (PA28-180)