there is timing marks on the gears. the servicemans reference has this procedure listed. there is a threaded plug you remove to see the mark on the magneto gear.
if you have got a copy of the parts book, operators book and servicemans book your up the proverbial creek without a paddle. if your a paid up member of acmoc you can view copies of the manuals we have in the tech library which is growing all the time thanks to a couple of dedicated vollenteers and those who have sent info to them.

you can get hard copies from the cat publications site, flea markets and ebay. there is a mob on ebay that sells reprints some of them are poor as the source copy wasnt that flash but better than nothing at all.