RE: cleaning the GX-15 engine
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