Hello
I have just acquired from my brother an old 1977 kz650B. He got it from a cousin who had ridden it for 5 years without any trouble. My brother rode it for two weeks and it died and has never run again.
I have changed the oil & filter, air filter, plugs and points. It gets air, gas and spark, and yet does not turn over. Even a shot of ether will not ignite. I am thinking that the coils may be bad. Before I sink lots of cash into a free bike, please anyone let me know if I am forgetting something. It has been a while since I dealt with one of these old machines.
Thank you.
Rich

See if you have voltage to coils with key on. I would get service manual, it will show
Primary and secondary resistance of coil windings.
You probably didn't loose compression all at once. Leaves you with fuel or spark, at the right time. Any rust in tank? Verify no water in bottom of float bowl.
Maybe try a quick blast of starting fluid, while cranking, don't try to run like this, you just want to verify you have spark. Then you know it is fuel problem.

I am picking up the manual from him today. I will need to pick up a meter for this part. The starting fluid had no effect. He had been riding the bike when it stopped working, and he already had taken care of the fuel issue.
I had not remembered about water in the float bowls, but I will check.
Thank you.

They float bowls will also reveal any rust or contamination.
It now sounds like spark problem. You can remove point cover, and with key on, manually open points, coil should fire(or if open, momentarily jump points.)Don't force closed, or adjust yet.
For the coils to fire, you need voltage, coil, capacitor. Spark plugs?
Many 4 cylinders use 2 double coils. One may provide spark for cyls 1+3, the other 2+4, or something like that.
One cylinder will fire on compression stroke, the other on exhaust stroke.
Check kill circuit.