Lars

I've had this 1981 Suzuki GS 450L project bike since spring. I had it running at first but since have been having trouble with the ignition. It had been sort of hit or miss beforehand, but when i put on the gas tank it stopped working all together. I figured the wires could have gotten screwed up from the tank so checked all the wires that have to do with ignition as far as I could tell, but all are continuous. I have a clymer manual but it doesn't really help with the problem. I know little about the ignition systems on these older bikes; what tests can I run to diagnose the problem?
Thanks for the help!
-Lars