Generator wont kick in until 1500 rpm's.

[B-O-B]

Do you have a growler to check your armature. I would think as long as the field windings are not grounded out they should be OK. Do you have any glyptal (red insulating varnish type paint) Check the brushes & bearings & brg housings & if all are ok you might turn the commutater & under cut between the bars spray windings with glyptal & put er back together should be ok