what is the best way to clean the grime off the inside of me GX-15 engine from kyosho ?

Kevin,

Try to do as little disassembly as possible. I take the back plate off and put a little light oil like sewing machine or automatic transmission oil in it. Then I swab inside with a Q-tip and kleenex's, and/or napkins. Try to flush the engine well with the oil and clean until you get no more dirt on the Q-tips or Kleenex's.

I put more oil in the engine, I then clean the excess oil from the engine as it seeps out later.

Enjoy,

Jim