Hmmm... So the 4 stroke RCV90 bears some resemblance to the E25 Sleeve. The difference being in the RCV the sleeve is on a rotary gear and the E25 it is a crank pin and socket. Aren't engines wonderful? You're right they are a strange animal. I can't conceive of the dual sleeve Aero Knight engine as being very practical - heat transfer must have been a bear - and the machining tolerances - ouch, yet it ran and was successful product.

Sometimes we think if something is CNC machined - the tolerances will be better than can be realized by a machinist. So obviously superior is modern technology we forget that the CNC is only following the pattern a programmer taught it. Witness the fact that a skilled machinist 60 years ago held tolerances as good as or better we can hold them today!

John