Motorcycle Repair: 81cb750k, check voltage, altenator

Question
I have a 81 cb750k that will not keep the battery up.I have replaced reg-rectifier and altenator brushes,battery, checked and cleaned ALL connections from switch and headlight back.Still only have about 12.6 volts when min.should be 13.4.ALSO after bike is ran and warm will not
turn starter over(battery up)lights are burning bright.Should I look for a starter selenoid
problem?
Thanks for any and ALL HELP!
Jim

Answer
Jim, check the restance values on the rotor COLD and HOT. These bikes tend to go open or high resistance when the rotor gets hot.

Could have a hot starter problem or solenoid issue. Check voltage at starter post when cranking, if close to battery voltage, then do a current check with inductive meter. You can jumper across the posts with a screwdriver to bypass the internals of the solenoid, just to see if it is starter or solenoid. Makes a lot of sparks, though.

Check with www.electrexusa.com site for more info on charging systems.

Bill Silver