[Dirtrack49]

Dean, you have it right! Interesting observation.
A lot of guys on experimental aircraft these days, like my RV4, use one mag and one auto electronic ignition on the other set of plugs. They claim that the engine runs more efficient and you still have the redundancy.
Chuck, the 90 hp Franklin is a 4 cylinder flat opposed engine like the Continentals and Lycomings of the same era. Probably weights....I don't know off hand. Maybe 230 lbs. if I were to guess.