I was doing carb synch'ing. As I reported earlier that "when I pulled right cylinder spark, engine died", mercury bar for the right cylinder was way higher than left. So I was turning the synchronizing screw on the carb and as I got both mercury bars close to even height rpm went up rapidly went up. I got surprised and turned the synchro screw on the carb opposite direction rapidly. Engine slowed down quick and began to bog down. From this point, I was not able to recover the bogging engine by turning the synchro screw in opposite direction and it fell below 8000rpm and died out. I restarted the engine but never fired up.
I pulled sparkplugs out and found both cylinders not flooded. No fuel lines were pinched. All the vacuum hoses were connected without leaks.
Only after I unhooked the carb sync from the motor, it fired up.
What would have caused this?
I think you ran out of gas, and turning the synch screw a lot after the readings were close to the same was a mistake, as was letting it run at 8000 rpms.
Be careful, deliberate, and thoughtful about everything you do with your bike. Plan everything out beforehand. It seems to me you're winging-it quite a bit. You'll learn more about your bike more quickly if you eliminate variables and take things one thing a at time.