I have a Jensen #35 and have wondered why there is no
exhaust choke. The Burnac Vulcan, along with the Mamod SE2,
use a 'choke' as a throttle. The throttle/choke on the
Burnac seems to have a better range than that on the SE2.
The exhaust port exits toward the boiler and the other
side was tapped for the thumbscrew. Screw in to slow
down and out to speed up. I added an end-of-post photo
and YouTube video demonstrating it. Maybe you can mod your
engine and add a choke. You just have cogitate on it a bit.
That's what I tell my wife I'm doing when daydreaming.
https://youtu.be/SRrwuH-0PzUGood Luck,
Wayne