Richard,
I am not familiar with the Bosch magneto as ours is the Eisemann mag. Might be a replacment for the Eisemann. Somthing like fuel pumps can be a.c. or carter on the same engine, Both work equally well. The Points seem to give the most problem in any point type ignition. Cleaning the points may solve the missing problem or possibly the spark plugs are breaking down under load.

We are quite new to the old machinery but enjoy it. and somebody else who knows more then I do might post a more defenate answer.
I hope this bit here helps.
Dana Reid