+10 to what Bibio says.
I asked a similar question about having to re-jet when I wanted to and have fitted a shorter"Slip-on" exhaust.I heeded what Bibio and others on here said and went ahead on my Curvy and have had no fuel delivery problems except that I tried a set of,"Iridium" spark plugs and my Curvy didn't like it,ran lean.Went back to Standard plugs and all good as I couldn't be bothered to mess around with the Mixture screw/s.
However I also have well balanced Carburetors.I bought a, Morgan Carbtune2 over ten years ago and it's still like new,
http://www.carbtune.co.uk/carbcust.html
http://www.carbtune.co.uk/
I get over 150 miles before my Fuel Low warning light comes on which is fine by me but I do give the fuel a shot of RedX from time-to-time