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

I can’t seem to locate the video just now. Maybe someone else knows?  In any event, what the guy did was install an adjustment mechanism, essentially a screw and link attached to a mount, parallel to the crankshaft, on the Governor side, linked to and providing adjustment of the rpm at which the Governor is freed so the exhaust valve can operate. It’s the same effect you get by pressing a finger against that arm when running.  He did it in a horizontal engine, the adjusting screw in front of the flywheel. On a vertical it’s end up above the flywheel.
He also made a swing mount with an adjustment screw for the ignition pickup. Turning the screw swivels the mount plate, adjusting the turning point from TDC to about ten degrees advance.  He claimed performance wasn’t changed a lot by that, but it did clean up the exhaust, which indicates better burn. 
If I find the video I’ll post a link.