TOPIC:

Could be the ignitor. Did you confirm that there is no spark at all on all four plugs? Check for spark in a dark room. If you lost a coil that wouldn't be super unusual. But to lose two coils at the same time would be very unusual.

Good idea on checking in the dark. When I checked it before I saw nothing, but then again it could just be because the room was lit.
The bike hasn't run since the early '90s...maybe that's why both coils could be bad?

The secondary wires are the ones that go from the coils to the sparkplugs, the caps that fit over the spakplugs can also go bad. A quick test with your ohm meter should tell you if they are good or not.
You should also test for voltage coming into the coils with the ignition switch on. With a good battery, you should have 12.5 - 13.5 volts. The fsm has a good diagnostic section for this.

Okay, buying a FSM today.

Some simple stuff.
Redo the spark plug wire connections at all points. if there's the white crusty oxidation, nip off the ends a tad. Or go ahead & replace the spark plug wires. Redo or clean other electrical conns. as well. simply disconnecting & reconnecting helps.

Coils. If you get the engine running, a simple check is to ride the bike at highway speeds, then stop & feel the coils. press hard with your fingers. they should be warm, not hot. My bike developed a high speed miss & I found that the coils were getting very hot to the touch, so I replaced them.

Battery. The motorcycle needs a good battery to run right, so make sure the battery is good. test it & do a load test. The bike can run poorly, especially at speed, if the battery isn't up to snuff. There are easy charging system checks you can do.
Ctek US 0.8 smart charger. VC97 digital multimeter. Scorpion AGM battery.

You can download the full KZ750 manual at this link, including supplements for the later year bikes. The ignition section should be very similar if not identical to that in the shaft drive manual.

www.750turbo.com/manuals/GPz750_Base%20Manual.pdf

Wish I had seen this before I bought one on eBay! Haha

Thank you. I'm not sure that this is for my bike though? I checked the back page and I believe my bike is the KZ 750 F1

Having the correct FSM is best. better still if you got it for cheap. You could get by on some stuff with that chain drive pdf, but the fork info will be incorrect & the chain drive manual doesn't have the shaft drive maintenance.

The reason I posted that chain drive 750 manual is for the info about the ignition system. I'm pretty sure the info is basically the same as the same section in the shaft drive manual. Shows how to check the coils anyway.

Yes, I agree. I mentioned that pdf earlier in this topic, but it was a long & wordy reply so he may have missed it. hee.

Yeah, good point. I'm hoping that it is the spark plug wiring. Coils are quite expensive. But I'll check.

Thanks for all the help, guys. I literally could not do this without it!

Hi Fish. Do you still have the '83 750 LTD Shaft. I just got one, and searching the net for information came across this post. Id like to hear the story of your bike. Attached is a pic of the bike as it was advertised when I bought it.