having no air filters might be a factor right
It sounds like the motorcycle has individual pod filters. or will have them. Do you have the stock airbox? If so, I would install the airbox w a new air filter. and check & set everything as per the factory service manual. troubleshooting isn't my forte, though, and don't relish the idea of trying to chase down why it won't start.
1981 KZ650-CSR. Competition, Sports & Road.