No, only fires on compression. Are you thinking of a 2 stroke engine maybe? The other thing that comes to mind about your bike is ignition timing. It might be firing way too late after the power stroke and more towards or ever during the exhaust. I haven't messed much with the ignition on these v's so I can't tell ya what to look for but typically the pickup coils and magneto (not sure that's the correct name on these) timing can be completely hosed if the pin that locks the magneto position on the crankshaft shears off throwing the spark timing into oblivion. Could also be valve timing although I doubt it, but in that case I don't think the engine would crank smoothly at all and might make a ghastly noise too. I'm just guessing with some scenarios to look at. Curious, When you
crank it does it spin smoothly or hitch and Buck like someone jammed a pipe wrench into the works?
I don`t like to contradict you Dave, but I believe the plugs should fire on every rotation of the rotor magnets past the ignition pickup coils. Not sure that it matters if there is a waste spark during the exhaust stroke though.
The vn750 does not have a magneto, but an electronic ignition system that is not adjustable for timing. Timing can be checked with a timing light though, by taking off the stator cover.
A compression test of both cylinders will help confirm or eliminate some possible causes of the symptoms I think.