today on my way back from work i noticed while i was waiting for a traffic lights to go green a little backfire when i tried to rev hard it in neutral than i rode it for a few km's and after i accelerated fast to overtake few cars it started to stall. i puled the clutch leaver and it went dead.
after i released clutch it started heavily like only one cylinder is running and idle was at 600rpm. i stopped checked everything seemed in place.

than i started it and rode it for a while to try to get home and than it start running normally i even pushed it a little harder to 7k rpm i pulls like hell. when i arrived home i checked fuel level cause my fuel gauge does not work and find out that i got less than 2 liters.
is it possible that one carb went out of fuel while hard acceleration? and could low fuel level in carb cause backfire ?

 

Sounds to me like you may have a clogged or partially clogged pilot jet in one of the carbs. I had the same problem a couple of years ago, and it would come and go (just for a minute or so at a time) until I ended up with a dead cylinder and heavy backfiring in the middle of a ride.

A careful cleaning of the carbs, including removing and soaking the pilot jets in carb spray, took care of the problem.

With the fuel mixture too lean to fire off the spark plug (lean misfire), the unburned fuel gets pumped through the cylinder and then burns when it hits the hot exhaust... BOOM!

 

ok thanks. i was avoiding to mess with carbs but at the and imm gonna have to.
i started it few minutes ago and it worked fine even with hard throttle in idle.

is it hard to fix carbs ?
i do know lot about mechanics but i always hated carbs and electrics.