SAVAGEJIM

A power drill would be required. Hobby-grade roto starters in most cases are poorly designed and made of poor materials; thus teeth stripping and all.

For these two .18 engines coupled together, a power drill will have the torque to turn them both. But unfortunately, the stresses will nlly be transferred downstream: The roto back plate could fail (the teeth in those gears strip instead), or the coupling gear that connnects both engines together could fail thus only one engine starts and the other will never start again until that coupling gear is replaced.

I would hole that instead of cheap cast gears (which is inadequate to even start a single cylinder engine in many cases) that this engine has hardened steel gears instead.