For the past year I have been trying to get my Benelli sei to run properly, I have bought new jets for the carbs balanced them with vacumn gauges but still to no avail. But this weekend I decided to recheck the carbs and check the slow running jets still not running right. Having satisfied myself that the carbs were ok I decided to look at the ignition timing. When the bike has its throttle opened rapidly it backfires then increases revs so is decided to retard the ignition about a degree.this made the problem even worse so I decided to advance it 2 degrees when I snapped the throttle it revved up with no hesitation.
The lesson I have learned is that some times you need to recheck things even if you are sure they are correct. I had fitted the ignition about 18 months earlier and it was not correct causing me to try other things when the only problem was timing