As combatpig alluded to, there is no need to take the engine apart this far.

I have planted a couple of engines, where dirt has gotten into the crankcase.

I take off the carb, back plate and head cover and liner.

Wash everything in soapy water, again with soapy water, then flush with an old jug of glow fuel, followed by WD40, and again more old glow fuel.... compressed air, and then I lightly turn the bearings over looking or feeling for any resistance or grittiness.

If I feel ANYTHING, I will stop and repeat the whole process, gently moving the assembly as it is being rinsed.

Once done a new gasket is installed on the backplate and head, and the carb is also seperately cleaned.

With the carb I also remove the nipples to assure that there is no hidden debris under them and use compressed air to blow out all of the orifaces.

Doing all this takes about 15-30 minutes tops and the engines have run just fine afterward.