parts for a streetfighter!

i bought a 1986 gsxr750 to replace my poor lost TL (i know some of you may think thats a step backwards but its 190kg with 100bhp at the back wheel, i'm not complaining), and its been going great till just a couple days ago. well pretty much yesterday though sunday was a little glitchy. feels like its running on 3 cylinders, maybe even two sometimes, pulled out sparkplugs yesterday, they're brand new. mechanic mate said, might be distributor leads but i'm hoping its not cos it turns out they're not cheap, and then he asked had it ever been left out in the rain? probably not, seeing as the previous owner was a fanatic..but i simply don't have cover for it. it does KINDA feel as if there's water in the engine, my NC24 was notorious for leaking water into the tank so i have experienced it before..
anyone got any tips? does this sound familiar to anyone? help would be greatly appreciated as it's currently my only means of transport, car needs wof and reg.