I purchased a 1999 1/2 red button 500 new in early 2000. I have done extensive modifications every winter for the first 8 years after initial break-in. Even before changing out the carb tuning jetting etc. It would backfire through the carb occasionally when starting, sometimes blowing the the carb and rubber adapter (stock unit) off the head leaving the carb hanging by the cables, pretty funny at the time. Any way I switched to an Amal concentric which I prefer, but still experience the occasional kick back. Next I tried electronic ignition same result. The dilemma now is my knee can no longer take it. Solution is to go back to points which I have plenty of experience fiddling with but also much easier to set the timing spot on, something that I haven't figured out how to do with an degree of accuracy with the electronic set up. So my question is are there different timing specs for the bikes marketed to the US as opposed to less restrictive countries. My 99 is as close to British as far as DOT crap and all up grades where made in the interest of dependability and rideability, right side shift- alternator upgrade with headlight, Amal carb, gearbox sealed bearings, steal paneers, recirculating crankcase breather, K70's Last but not least I put a new forged piston replaced clutch plates Now I would like to double check to see if any one has experience with this old school engine and any knowledge about timing differences if any??? Thanks Mike in MN.