I have a Coleman Vantage 3500 motor runs no generator output

This sound like a loss of residual magnetism in the generator. The field will need to be "flashed".This is also known as re-exciting the field of the generator.
The Coleman manual gives these steps:
1Use a 6 Volt lantern batters (dry cell) or a 12 Volt automotive battery.
2.Disconnect all loads from generator.
3. Remove the brush cover (that's the rectangular plastic cover on the end of the generator.)
4. Plug a lamp or light into the generator before starting the engine. The light will illuminlate when ?Voltage has returned.
5. Start the engine with no load connected to the generator.
6. Attach the "-" lead of the battery to the negative brush. Very briefly touch the "+" lead of the battery to the positive brush. Remove as soon as Voltage builds up.