onan 7000 watt marquis

Found it! At least for our old BFA "4.0 RV Genset" which was twin-cylinder opposed 1800-RPM. Parts list shows Flywheel with four holes around the crankshaft hole. A Steering Wheel or Vibration Damper Puller (with the correct capscrews to thread into the flywheel) should pull it. You'd back the bolt holding flywheel to crankshaft out a couple turns and let the puller bear on it. At least that's how the pic in my manual looks. Of course the design could have changed. BFA was an old machine.

NOTE: OP seems to indicate that the flywheel is between Engine and Generator sections. The gensets in my manual have the flywheel in a blower housing at one end of the unit, not between the sections...

I tried to find something in the manual I have for an older BFA and couldn't find anything about this removal.

But let me offer a warning: Be sure you have torqued the flywheel back down before you do anything that could lead to a cylinder firing. This will break the flywheel at the keyway. Torque it first!

donq1576 wrote:
how do you remove the flywheel from the rotor rotor number 201-3388-s3 it is on a onan 7000 watt marquis

I had to buy a steering wheel puller.

Moved from Forum Technical Support

Have never done so but....
Most cases, the flywheel will have two smaller holes about an inch or so from the center of the flywheel. You find a couple bolts that size and a puller (NAPA) and use that to remove a pulley or flywheel.
Again, I'm guessing that is the way yours comes off. But you didn't get any answers so its something to check.