Here was a response to an old GardenWeb electrical question about the output of a portable generator. The member who asked the question did not make a follow-up to tell if the problem was solved. There was no output from the generator.
Field Flashing of Portable Generators
This tip comes from the Briggs & Stratton Customer Education Department. As an alternative to flashing a rotor winding with a battery applied to the brushes, an electric drill may be used. Follow these steps to flash the generator:

* Plug the electric drill into the generator receptacle. (Cordless drills do not work)
* If the drill is reversible, move the direction switch to the forward position.
* Start the generator
* While depressing the trigger on the drill, spin the drill chuck in reverse direction. This will excite the field and the generator will now produce electricity. If spinning the chuck one direction does not work, try spinning the chuck in the other direction as you may have the reverse switch positioned backwards.

Use caution not to get your hand or other materials caught in the chuck. As soon as the field is excited, the generator will produce power and the drill will turn on.

The reason this works is because the electric motor in the drill will act as a small generator when spun backwards. The magnets in the drill's motor induce a voltage into the motor windings, which is fed back through the trigger, cord and into the generators receptacle. From there it goes into the power winding of the stator. The voltage going through the power winding creates a magnetic field, which is intensified due to the iron core of the stator laminations. The rotor intersects this magnetic field as it is spun past the power winding, thus inducing a voltage in the rotor winding. Once current flow is present in the rotor winding the rotor has been flashed.

If flashing the field does not make the generator work, you may have additional problems, besides a lack of magnetism in the rotor. Further testing will be needed. Hopefully, this will give a simple way to field flash your generator if needed - Bruce Perrault perr.com

Here is a link that might be useful: Gardenweb generator question

Sorry, I didn't include this bit in my response -- the generator in question was a Generac 5500.

Thanks for the tip. After I check the brushes I will try it.

Pulled the brushes but didn't notice any problem then reinstalled them. Started the gen. and did a voltage test and now have 240 so one must have been stuck and hoping not just a coincidence.Thanks to all that replied.