Preacha

G'day all, New here, been riding and tinkering for 30yrs plus, have come across a problem with my XJ900F 1985 Model, that has me stumped. Been through all forums, seem to be the answer then when I try the solution same problem. Clean plugs new fuel, full choke bike starts and runs well, try again next day, sort-of starts on 2-3 cylinders, after 4 -5 goes at stopping and starting, won't start, backfires occasionally. Clean the plugs sorts problem for the above mentioned period. If I test the spark with the trusted screwdriver Plug lead via screwdriver to rocker bolt, awesome spark. Any help much appreciated.