84 Honda VF750F ignition problem

The bike will start right up when dead cold. Seems to only run on two
cylinders with the others kickin in and out. After about one minute or
less the bike will die and not start back up. I get no spark showing
with my inductive timing light but a spark plug setting on the frame
does show spark. I have tested teh coil and they fall within specs
with the ohm meter. I have also tested the spark generator with the
ohm meter and it reads 488 instead of 480. Seems close enough to me.
The spark box units are not testable according to my book. I have
been quoted 95 for each spark box and 55 for the generator. Since I
have never rode this bike I am not interested in spending 250.00 bucks
just to seek what kind of shape the rest of it is in. Anyone have a
good idea if its the spark generator or how I can test the spark box
units?

 

After playing with the choke and throttle when its cold I get the bike
to run on all 4 and rev up. I can hold the RPMs up for a couple
minutes. Then when I try to ease off the throttle dead. Just like you
hit the stop button. Bike will not fire again. I tried starting
fluid to rule out fuel problems. No difference. I did get the bike
to fire back up and run on two cyclinder for less then 10 seconds. No
tach. This bike does not seem to have a fuel pump. If the spark
generator was bad would that also affect the tach? or does it seem
like I could have two bad units. After the bike warmed up a bit after
the hi rev startup I tested the spark generator and it was 580 ohms on
one side and 520 on the other. The book spec is 480. So I am pretty
sure that is bad and that is why the bike just turns off. If it was
one of the spark boxes or carbs I think it would struggle a bit before
stopping. Any suggestions?

 

I have already scotted and found some for $55.00 right down the
street. A couple of places were only a bit cheaper then I would have
to pay for shipping and wait. Thanks for the input.