Motorcycle Repair: Intermittent Problem with 1987 FXRS, pickup test, fxrs

Question
Hello, My 1987 HD FXRS runs fine until the motor gets to full operating temperature. So far I've cleaned out the fuel tank, installed a new fuel line with an inline filter, rebuilt the carburetor, installed a new coil, new battery. The bike starts running on one cylinder and then dies.  Could this be the voltage regulator OR the ignition sensor/rotor cup?

Any help would be greatly appreciated,

Thank You,

David Karow Jr.

Answer
If it were your voltage regulator your battery would not stay charged.
First, test the charging system. Start the bike and at the battery, you should be getting around 13.5 volts at 2000 RPM.
If thats ok then test your spark pickup. Test it cold then hot. They have been known to fail when they get hot.
Good luck and happy riding
Mike