ORIGINAL: Mr67Stang
I would just like to add... make absolutely sure it is securely mounted and restrained. I have 6 stitches in my finger right now from an unrestrained bench test about 4 days ago now. I am going to vote for mount it in the plane from here on out.
"Unrestrained?" You started an engine without it attached to
anything? I'm truly sorry for your injury. I guess you won't do that again.
I built a test jig from a piece of plywood, with hooks to attach the fuel tank with rubber bands, and a throttle pushrod and lever. It takes interchangeable "engine mounts," so with any new engine that doesn't fit the same holes, all I have to make is a new mount from another small piece of plywood.
I tightly C-clamp this to a full size picnic table before starting an engine. These things really pull! Make sure your plane is secure if you're going to run in the engine in the plane, too.
Phil