Ignitoin query

[comedybob]

I just bought a 1982 Suzuki gs750. I took it into a shop to have it looked at. Mechanic wanted too much($1200) to get it running, so I took it home. When I tried to turn it over to check the spark, Lo and behold, the bike only turns over with the key in the off position, or past the run position in the auxiliary position. Turn the bike to on, and i have lights, horn etc, but the engine won't turn. It's not a short, because when I hit the starter, the lights don't dim, there's no electric crackle, no indication of a short. Any ideas where I should look? Thanks
bob

[BrokenSprocketGarage]

Ignition switch