Why gearless two wheelers are not fuel efficient?

It will depend upon the liking & fuel economy too. The moped or scooter with no gears is definitly suits to ladies especially, because you have a option of button start fascility in mopeds. Where as this is rarely found in geared vehicles. Ladies have a kick start problem, as they have little muscular power, and neither like kicking naturally as like males. This and main reason supercedes the fuel economy aspect when the females are going to use the vehicle. But for males the speedy, geared bikes, especially the latest four stroke engine bikes with disc brakes are very much best. Ofcourse geared vehicle has a higher fuel economy. A gearless moped will hardly run for 40kms per liter of petrol and a geared bike as i stated will run for 80 to 100 kms per litre of petrol. Now it's up to you what to given priority. Wish you a enjoyable ride on life with your spouse.