Theres one in every crowd.
Someone who thinks he knows everything.

I reread the operating instructions again and it says....
one servo to control the steam supply BY A VALVE and to act as a throttle.
The second servo is used to reverse the engine.

It also states
"the reversing lever is NOT intended as a speed control, but CAN be used to increase efficiency when running with a light load"

SO I will ask again
What is this valve called? and where can I get one?

PLEASE if you dont know then dont say!!!
ONLY intellagent answers please!!!