Hi Andrew,
But if you replace the cylinder, glowhead and piston with something more modern, it will no longer be a Thermal Hopper and you won't have the "Thermal Hopper Experience"!
Let me explain what the "Thermal Hopper Experience" is:
As a young lad in the 50s, my mate and I flew 1/2A airplanes powered by our trusty old OK Cubs. My mate's paper route supplied sufficient funds for him to buy a new engine... the just released Thermal Hopper. Yes, we read all the hype about this engine's performance but were skeptical.
We removed the Cub, installed the TH and went out to fly without even running the engine on a stand (the ads said it didn't need breaking in). Contrary to the oft cantankerous Cubs, the TH fired up right away which startled us but when the needle was turned in to a good 2-stoke, I knew I had a tiger in my hands... What a sound and what pull!
I launched the plane and it spun my mate around so fast that after the flight, he fell down... now that's performance and the TH Experience... you never forget it!
Orv.
Orv.