monkeyboyr6

have just started my race bike after doing engine rebuild. only firing on 3. have tried plug swap and coil swap, these have been eliminated as a fault if i pull plug cap off while engine is running it has no effect on idle or running but other 3 cylinders will stall the engine if i try this. when i pull plag cap off 1 it arcs everywhere and gives me a belt ! other 3 don't do this. bike had been standing since autumn before rebuild. gave battery bit of a charge. do they need a certain voltage to run the ignition system properly ? i think it's 12.8v but surely this would affect all cylinders. like i say have tried plugs and coils and these are fine i am puzzled, any help greatly appreciated. p.s bike runs on total loss, no charging circuit