info needed

I have an Onan modle W3M upright 2 cyl. water-cooled gen. of the 40's vintage, does any-one know how to time the mag? There arn't any timing marks on the gears.

Leon: this is copied directly from the manual for my W2C. No 1 piston must be at top of its comp. stoke and TC marks exactly in line, (TC marks on crankcase and flywheel). Set breaker points at .20 (.15 for Wico), turn mag in direction of normal rotation until impulse just trips with the distributor arm pointing to No. 1 tower. Install mag without turning gear. Turn engine slowly and note whether impulse trips when TC marks are in line. If not to far off correct by turning mag frame slightly, otherwise turn one tooth more or less.