ZN1300 wont start

I am working on my '88 ZN1300, but cant get her to fire. I have fuel flow and spark. Problem is I am getting a code 23 and it failed the Starter Signal Test. I try to start and it will crank, then click, then weak turn over. The battery is new bike bandit unit, but dont know what CCA is. I tried to jump with my car (not running) but same thing.

I did get it to start a few months back, but now nothing. Nearing point of just parting it and trashing what doesn't sell.

thoughts?

I had a similar problem on my 1984 ZG1300, it was a few problems all to do with corroded connections, I was getting a spark and fuel to start with but it wouldn’t fire on all 6 evenly and would drop off after a minute or so,

The computer flashed a pickup coil fault so cleaned the connections up and first problem solved but still would not run.
So I started a systematic testing and cleaning of all the connections linked to the starting system using the flow charts ,the multi plug to the computer had 3 or 4 wires that had heavy corrosion that could not be seen until the wires removed from the block and cleaned, they also needed to be nipped upas the connection was slack. I also found other wires that needed cleaning when removed from their blocks.
Once I had done the cleaning and got the computer sending and receiving the correct signals
By this time the fuel pump stopped working, I found that the main relay which also controls the starter system had failed as well, once a replacement relay was fitted the fuel pump activated I then put the tank on connected the lines, when the starter was pressed the bike fired on all 6 running perfectly.
I hope that this will help, before giving up it is worth spending sometime checking the connection

A word of caution regarding jump-starting, Bri-Guy-GA. I once witnessed somebody jump starting a Honda CBR600 from a car, and the bike's battery belched some of it's electrolyte out through the breather. I guess the - much higher - amp hour rating of the car battery overwhelmed the small bike battery, and "boiled" it. Maybe one of the experts on this forum can confirm this, or tell me I'm talking b******s!
Please don't give up on your 1300, though.

I've jumpstarted many bikes from a car with no issues at all. The thing to remember is to NEVER start the car while connected to the bike. A cars alternator puts out more juice than a bike stator and you can fry the battery or regulator or both. Don't leave it connected after starting since your bike will now try to charge both batteries which may fry the statorl.