Out of interest how is your battery? I'm on with a very similar problem on a GSXR SRAD resto at the moment, spark is visible when doing a test but she's struggling to fire but does get going eventually one cylinder at a time then runs fine, but she's an absolute bitch to start. Carbs have been cleaned properly. The current battery was dead when I picked the bike up, battery tender brought it back to life but I think it's toast, new Motobatt going in this week. I think the spark is weakening under compression and when the starter is also sucking juice.
