ORIGINAL: William Robison
You are aware the VT21 and VT49 atre both available brand new, made in the USA?
Bill.
These old HP VT-21 4stroke engines was manufactured in Hirtenberger Patronen-Zundhutchen und Metalwarenfabrik AG, Hirtenberg, Austria.
These engines was smallest 4stroke engine at marked and was released in 1983, are not sure when the production was ended.
The power are not big, 3.463 cc, 0.238bhp at 12250 rpm. But it run faster than poppet valve 4 stroke engines.
The engine are old, but not important, all works well so long you take care at engine. And do not worry about you flies with old engine, I am using my Webra T-4 from 1980 and works well as new and a lot of peoples around me when i am running the engine, some of them said to me, why engine has timing belt..
then a surpass .26, then a FS .20, but none could come close to the low fuel consumption of the HP .21!
Cause the HP VT-21 has higher compresion ratio at 10.5:1 while OS FS20 has lower compresion ratio at 7.2:1 , but OS FS20 are more powerful in effect/volume. More compression ratio=less fuel , it is a problem if more compression ratio, fuel will detonating, there is difference combustion camber in each engines and has own compression ratio as engine constructor has tested and found which compression ratio are suitable for this engine.
Jens Eirik