I have several of these engines, but not a 21 cc. I have 2 - 23 cc, 2 - 26 cc and a 63 cc. Have only converted one of the 23 cc. They are easy to convert, not too much metal has to be removed. The crank case is arranged so that you could use a flat plate for a motor mount or just bolt directly to the fire wall. The 23 I converted is set up for glow. Exhause timing was changed from 120 deg to 160 deg. Intake timing changed from 100 deg to 108 deg. The port timing was kept the same, gut the ports were raised 30 thousands to compensate for the 30 thou I took off the base of the cylinder. The piston was crowned to accomodate the shape of the combustion chamber. I'm using a Walbro 11 mm carb with the low and high speed passages enlarged by 50% of the crossectional area.

Only a couple of runs so far, but on a 16 X 6 power point it was running about 11,000. Fuel was powermaster 10% nitro. that was way too much oil, so I'm going to mix some with 3% Klitz and 10% nitro.