geo, How do you know there is no spark? In other words, how did you check? To check for spark, pull a plug and put the tip NEAR the engine. Turn the bike over and you should see spark jump. Do you have a four cylinder or twin KZ750? It kind of makes a difference when providing advice...
If you are right and there is no spark, there are two reasons why this might be. One, the ignition isn't working or Two, there is no power going to the coils.
Let's take the second reason first... no power. It doesn't seem likely because the bike turns over. The power that triggers your starter relay goes from your main fuse, through your ignition switch, over to your right hand kill switch to the button that triggers the starter. Another wire comes off the kill switch right next to the wire that goes to the starter button and that wire comes out and goes through a connector on the steering stem neck and from there goes to the coils and provides power. If you have no power, it is easy to check. Turn the key on and use a multimeter. Put the POSITIVE PROBE on the lug on the coil where the power connects. The small 18 ga. wire connected to this lug will be either yellow/red, red or pink. Put the NEGATIVE PROBE on the engine cases (ground). Make sure you don't touch the positive probe to the frame or other ground while the key is on. You should see about 11.8 to 12.2 VDC with the key on and the engine not running. If you do, the power isn't the problem.
OK, that means if there is no spark, there is a problem with the ignition system. Since I don't know the bike type, I don't want to go through ALL the possibilities of a points ignition and electronic ignition... let us know what type bike you have. If it is a four cylinder, check for spark on #4 cylinder, then #3. A four cylinder has two coils where the twin has one so this would tell me a lot about where a possible problem lies.
