Have an 84 yamaha venture 1200 with no spark on the rear cylinders? need to know how to test what is wrong and what to look for. Can't find a 1984 yamaha Venture royal in the markings for Yamaha

Hello Mike...If the rear cylinders aren't firing I would start by checking for defective plug wires. Visual, for cracks and with an ohm meter for resistance. Test your coils, same principal, test to see if their is power to the coils. Your bike has a TCI box thats located in a not so good spot....that really takes abuse. This is "brain" a circuit board. It gets hot, cools down, and moisture inside is the result, over the years it finally gives up. The voltage to the coils travels through the TCI. If you aren't getting 12 volts, then corrosion, faulty circuit, leaking capicitors inside the "box" are at fault. I have heard of some riders opening the TCI, letting the sun dry it out and remounting in a different location, I have replaced several, on the early viragos. They have been discontinued. i found several on ebay, also i know a biker that can repair solder these, if needed.