I have finished tuning the 17.5 Dellorto Carb and am very happy to say that my last tank I got 77.8 MPG. I also found out that you must always have the bike in the exact same position or the amount of fuel you start out with will be different! Pointed down hill I got about 1 pint more fuel in. WHen I started out my worse mileage was 42 and when I went too lean I hit 96 Mpg
I ended up changing the Infuser which was a 210 back to the 209 and of course used the #40 Choke Jet and #25 Idle / Pilot Jet. In the end I ended up with a #82 Main with the Needle on the 3rd position and the Air Screw about 3 turns out. Good performance and I think the little extra Power now allows me to use les throttle Position to keep the Speed up hence the Better mileage.
BTW, My top speed is still 51.8 MPH because It is limited to the RPMS the engine can turn under power. Geared 28 front / 22 rear