i had the same problem with my b12 after magpalit ng gasket..hirap mag start, minsan ok yung idling, minsan namamatayan..parang kapos un gas, parang may hangin na kasama...3 mekaniko na tumingin, may nagbara daw, di daw maayos un pagbalik n carb, nilinis ulet un carb.. ...ganun pa rin, pabalik balik..until last friday namamtayan pa rin, the nearest talyer fr my work place was rapide c/o peter sa market, market..mali mali daw un kabit, may kinabit sya sa likod ng carb at the same time inayos nya rin un timing...so far..maayos na un idling.. 1 week na sya 1 click and di na namamatayan..and di sya nag pa charge, pang yosi lang binigay ko..