AFAIK, the ignition voltage comes from the 120V windings, but that's a part I've never had reason to figure out (yet ;)). They'd need to step it up to around 10kV or more for a spark plug. Again AFAIK, there's no separate winding or magneto.
The reason there's a delay in your 120V is not in the generator. I think it's in the transfer switch. My Tiger hasn't got one, and the 120V inside is live as soon as the Onan starts. Some RV makers choose to set up a delay to be insure the Onan is up to speed before any load is applied, others trust the customer not to start the Onan with the A/C switched on.
Clear as mud, right? ;) I've been futzing about with these dang things for about 12 years & three 2800's now; it's been a long, slow learning curve with some dips along the way.
Jim, "Why do gas stations lock their restrooms? Are they afraid someone will sneak in and clean them?"