Motorcycle Repair: FZR ignition problem?, mixture settings, yamaha fzr 600

Question
Falcon, I have a 1989  Yamaha FZR 600 and it has been giving me trouble off and on for the last year.  It will go from running perfectly to not starting the next day every so often?  I have replaced all of the plugs, caps and checked the ignition coils.  They are all fine however now I am not getting a good spark(or sometimes none at all).  The last time this happened I had just leaned out the carbs (they were running rich)and the bike felt fine; next morning it wouldn't start.  The bike is backfiring out of the pipe when I try to start it now?  My wires and pickup coil seem fine however my relay switch might not be right (opposite resistance ratings to what the Hayne's guide say's it should be).  Could a bad diode in the relay cause these symptoms, or could it be my digital ignitor?  Unfortunately I cannot test the latter and it is very expensive to replace.  Any input or advice would be greatly appreciated, this is driving me nuts!   
Conor

Answer
Hi Conor.
 If the relay is giving you readings that are not consistent with the manual, then repalace it.  That goes for any component.

 As for the CDI box, they are not known to go bad.  Fact is, you have a better chance to win the lottery than to have one fail on you.

 Fact is, based on what you have told me, there is a bad connection or an intermittent short in the system.  It could also be something as simple as a place in the wiring where it may be occassionaly arcing against the frame or engine.

 Leaning out the carbs was not the answer.  They are set at the factory and after the bike is fixed, it will not run right because of the new mixture settings.  Unless you are changimg to a non factory-approved exhaust or doing some other performance work on the bike, you should NEVER change the mixture.  Now they will need to be reset back to factory settings.

 Check the wiring for arcing and intermittent shorts (likely found near the steering head).

 Check all of your physical connections for the carbs to airbox and to manifolds for proper tightness and to insure that there is no air leak, which could cause the mixture to appear to change on it's own.

 Remember, an intermittent short will not make itself obvious, so you will have to jiggle the wiring during testing to find any.  Unfortunately, it is a time-consuming process.

Let me know what you find.
Good luck.
FALCON