Motorcycle Repair: Timing adjustment for 82 Kawa KZ750N Spectre, fuel mixture, adjustment screw

Question
I was reading through a chilton manual on motorcycles (general) and found in the troubleshooting section that backfire was caused by the timing being too far advanced (it was the only explaination for backfire).  I also read that this could also cause engine ping; well I'm experiencing both on my 1982 Kawasaki KZ750N1 Spectre and was wondering how to check and, if neccessary, adjust this.  Also, my fuel mixture is somewhat rich but according to a label under my seat, there is no adjustment screw (I still looked but only saw the three screws on the throtle rail, but aren't those for balancing the carbs?), how can the mixture be ajusted?  I just purchased the bike from a private seller and, unfortunately, don't know any of its history.

Answer
Hi John,

Go to this site and look at part number #16014. This is the air-fuel screw. It may be covered by a tamper plug. Remove the plug to adjust mixture. Finish by checking carburetor synchronization.

http://buykawasaki.com/Default.asp?strContentURL=Site/Home/HomeSplash.asp?

Your MC has electronic ignition. Timing is not adjustable. Likely cause of backfiring is improperly adjusted carbs, sychronization, or varnished carbs.

Respectfully,
Mark Shively