Motorcycle Repair: firing, honda 550 four, exhaust stroke

Question
My 76' honda 550 four is firing only on cylinders 1 and 4  what could be wrong?

Answer
Could be points, condensors or coil.  Cylinders 1&4 plugs fire at the same time and 2&3 fire at the same time.  One cylinder fires on the compression stroke and the other fire on the exhaust stroke. I'd start by cleaning the points and making sure they have voltage when they are open.  If that's not the problem, it's probably a coil. If the points spark a lot when the bike is running, you have a bad condensor.

Regards
Rich