Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Here is a simple way to add a speed controller to the M90. No need to modify/replace the gov. springs. It can be adjusted while it is running. I could get it to run slower if I adjusted the mixture for a more richer setting as I slowed it down. It is a 0.016/.4mm feeler gauge that adds an adjustable pressure to the lock out arm. The pressure counteracts the governor springs to lower the speed.

Also shown is  an easy way to mount the OEM engine wood base to a larger piece of wood. The bottom sliding cover is screwed to the plank with washer spacers. The latch is a loose washer.

Video link:

Thanks Nick! BTW, I love your singing

I forgot to mention a trick I learned from working on full size H&M engines. The exhaust valve spring has to be stronger than the intake valve spring because the exhaust valve may also be sucked open along with the intake valve. Replaced mine with a stronger spring and made it run much better.

There is an extended finger on the lock out latch for the exhaust valve. If you press on it while the engine is running, it will delay the release of the open valve. The feeler guage blade just adds an adjustable pressure to the finger. The more pressure on it, the more delay until it releases, and the slower it runs. The thickness of the blade affects how sensitive the adjustment is.

I often wondered what that finger was for; now I know! But maybe Jin could tell us what it was for.

A pic below shows the blade on the finger.