are you absolutely positive the rear cylinder is dead when cold from loss of spark....or...loss of compression? THE first tell-tale sign of heavy internal wear/burned exhaust valves on an air-cooled V-twin is loss of compression when the motor is cold.
simple to determine: just switch the plug wire leads on the coil then try to start when it's cold. if the rear cylinder now fires and the front cylinder is dead it's the coil. if the rear cylinder remains dead it is loss of compression. compression check and properly performed leak-down test will determine the source of the leak and why.
PS-if your response is "i can't do that because the plug wires aren't long enough" or something similarly idiotic then clearly you need to have a pro look at the bike.
Last edited by user_deleted; 01-19-2019 at 12:08 PM.
Buy that man a cold one 👍^^^^