big generators weight

Definitely more than your weight

When you ask a question try to explain the need , please don't post for the sake of asking something.

If you are buying it, it will be available in the manual, along with the lifting and handling requirements.

You are not likely going to get an answer on this site regardless of what information you supply. Simply because of the multitude of variables involved, amount of poles, winding material etc,

If you do not have access to any OEM drawings or instruction books my advise to you would be to get either some calibrated hydraulic jacks, or jacks that you know the size of the cylinders etc., Jack it up off the lifting trunnions and figure out the weight.

Other than that rig it for 100 tons and you shouldn't get into trouble.