To add to Montague's post...

If you ever do have an engine full of mud, take off the carb and glow plug, and flush the engine with that half gallon of glow fuel left over from last season.

Use a sprayer and paint brush to get at the outer surfaces and flush, flush, flush until all of the debris is gone.

I've even resorted to first flushing the engine out with water ( which is better to desolve the mud and debris ) then immediately follow that with copious amounts of old glow fuel to get rid of the water, etc.

Then I slowly rotate the crankshaft trying to feel any resistance from "grit".

If everything turns smoothly, it gets yet another flush and is put back together.

I haven't had a problem with this...