I have 2886 miles on my Viva MP250RO yy250tt
with the CFmoto 244cc Honda clone
The only problems that I have had are with the Vac fuel pump (recomend a 2psi to 4 psi elec fuel pump) and please note that the fuel pump works fine around town but I have 8.3 miles of my daily trip each way on an interstate with 70mph to 75mph being the avrage. Due to the fuel pumps being vac operated and full throttle being at 0 vac after afew min at constent full throttle a fuel starvation issue occors.
I avrage around 60 to 65 mpg and run at around 70 mph to 75 mph daily.
Fuel savings great, fun to ride
Around $2000.00 to your door

My Honda Reflex averages about 70mpg in normal city use, but still goes up to 75mph on the freeway. It will cost you about 5k for a new one, but used you might find one for 3k or so.

Over 150cc probably Yamaha Majesty would get the best mileage but you won’t get it for $2000… more like $6000.
For that price maybe check out Yamaha’s Vino 125. It’ll go around 55mph and get’s close to 100miles on an imperial gallon.

If you want to go over 150cc It’s actually cheaper to get a regular motorcycle like the 250Kawasaki ninja. ($4000ish)