My 84' 900 8valve turbo with K-jet developed this problem today. When the engine reaches 2500-3000rpm like when I hold 2nd or 3rd gear, it will will start bucking and jerking quite violently. I was thinking fuel pump but the engine load is quite low when this happens. With lower revs in 2nd or 3rd with a higher engine load, there isn't a problem. Does anyone have an idea what's wrong? Cheers!