Made from a 1" steam tee with a 1.250" bore x 1.750" stroke with a 5 piece crank, one day I'll try learning to turn a one piece crank. Viewing from the rear, the gear set on the left is for ignition and exhaust timing. The blue lever on the left is just an extention of the exhaust lever that's tripped buy the cam, I left it long because it makes it easy to hold the exhaust valve open to freewheel the engine. The shiny lever forward the blue one is the latchout arm. The gear set on the right is for the flyball type governor, which is a shaft in a shaft. As speed increases, the foot of the governor, which is part of the inner shaft, applies force to the latchout arm and when it meets the exhaust pushrod they latch.
I think everything else might be straight forward, 4" flywheels and balanced using nuts and bolts to the inside of the flywheels, the carb was built from drawings from another set of model engine plans, homemade sparkplug. Minus the tong, it's 16" long x 8" wide x 12" tall and about 30 lbs.
This project was greatly influenced by my good friend and fellow modeler, Bill Johnson. His knowledge on the subject came with great appreciation when those "Tight-spots" arose.