In the graph below, you'll notice the gradual increase in litres /100km from the very beginning. The engine was running excessively rich, at low to mid revs so the economy wasn't as good as it could have been. The increased fuel use was due to a build-up of carbon in the exhaust valve seats. As this increased in depth, it leaked more & more, reducing the cylinder pressure. Eventually, a piece of carbon broke out, reducing the compression to zero on one cylinder. At that point, the head came off, and the valves were re-ground. Also, at that point, I fitted the Motty AFR Tuner and new rings. The combination of excellent compression & a leaner burn resulted in a vast improvement in economy.
This happened again at the 95,000 km mark, so the leaner burn didn't fix the problem. It turned out to be caused by my use of mineral oil instead of synthetic. The additives in the oil attached to the cooler exhaust valve stems and as they built up, they restricted the valve movement, reducing their ability to seal. The slight leak was filled with carbon.
I learnt a valuable lesson. When Benelli specified a synthetic engine oil, they did it for a reason.

Economy Graph 0 - 75,000 km