Buccaneer,

Make sure you have a kill switch hooked up to the magneto in case it over speeds. Slow turning 2 strokes are controlled primarily with timing. I would suggest that you start out with the timing 10-20 degrees retarded and advance as needed. You fuel mixer dosn’t appear to have a throttle control so it won’t be much help in trying to slow it down. The stem being sloppy shouldn’t be much trouble as long the valve is seating. Sounds like your spring will be fine since it’s opening. As Tubs stated pulling thru compression is the way to start it. Bumping against compression is more of a buzz coil battery ignition setup starting procedure. If planning on running on a boat you will need to be able to adjust timing while running. I would suggest finding a magneto that is adjustable, or converting it to a battery buzz coil type ignition system.

Below is a link to a engine I have, that by design of the make and break ignition system cannot be retarded past TDC. In order to run it without a load, the throttle in barely opened to keep it from overspeeding. Restricting the air this much, causes it to cycle multiple times between firing.

Jim

https://m.youtube.com/watch?v=EI0k5zaj4X0