you can try removing the carb to have a look at your MJ, maybe
your prev owner change to 150 or 155 so it drink petrol damn
fierce, which i think is most likely.
BTW pgm fuel tap is known to leak, so even if u set it to on,
sometimes it'll use reserve. ever got once i riding using on, just
as i about to reach home, my bike suddenly si chia, i open tank
see, not a drop of petrol left, even reserve oso all gone.
u can also ride your bike around wif the tap set to off, just that
sometimes if u rev too high u feel abit no power 
simple solution is to buy the lockhart philips quick release fuel
tap. where buy ah? er.... ask around lah, motorworld, loois, max
equipment etc etc etc...
