[ProDigit]

Yup, you're right.
The rebel has a small performance edge over eg: the Suzuki TU250X;
I find the Rebel slightly underpowered for the interstate, when having a bit of headwind, but with a 10MPH tailwind, it performs more than admirably, even on the interstate!

A Rebel with a 249-300cc BBK, or the Rebel with direct fuel injection would probably be all you need to have sufficient speed (direct fuel injection adds HP over port fuel injection or with a carburetor).

For a thumper you'd probably be better off with a 350-400cc one.
Thumpers are better MPG wise, but they vibrate a lot, and usually give good torque, but less good top speeds.

I bet a 400cc thumper could do 90MPH tops, which is what a 249-275cc PTwin does as well.
One can then argue which one will give the better fuel mileage.

CC over CC, there's no argument over which wins what.
A thumper wins in MPG, and a Ptwin in performance.

But when comparing MPG based on performance numbers; a ptwin is both smaller, lighter, has higher performance, and therefor, if top speed are matched on both engines, the PTwin would have better MPG as the same performance can be gotten with a smaller engine. (eg: 250cc PTwin vs 350cc Thumper have both about the same top speed, and similar torque in the torque/HP band, but the thumper gets it's torque at the lower revs 2-4k rpm, while the ptwin gets it at usually 7.5k RPM.

For that reason, I believe thumpers are good upto 200cc.
They would make great and affordable small city bikes, but lousy highway bikes.
Too large thumpers are heavy, require more oil, and vibrate a lot more than a Ptwin engine (which needs a way smaller counterbalance).



To get 80MPG out of the Rebel stock, is quite an achievement.
I got 60-66MPG out of it riding it hard, and 75MPG riding it like it was made out of porcelain, stock gear.
Perhaps you're talking about 80MPG IMP instead of US?
80 MPG IMP equals 66MPG US, which is what I got stock out of my bike as well.
My current numbers of 88MPG US equal 105MPG IMP.
That'd be a 20MPG raise.

The Rebel fuelups so far have been:
1st tank 107MPG (US), might be because the next tank wasn't completely filled up, so some off reading there, as well as a bit of carb cleaner in the fuel might offset the value a bit).
2nd tank 88MPG, (tank wasn't fully filled); 50% highway and interstate riding with headwind probably the cause of lower reading
3rd tank 87MPG (was because the tank was completely filled to the brim; with some highway riding, and lots of start stop traffic.

Because the tank was filled a lot more than previous (I tried to squeeze $6 on fuel in it, the last $0.5 was overfilling it a bit), I might see an increase in MPG on my next tank.

I'm expecting 95+MPG on my next readout (that is 115+MPG IMP).
I'm expecting to have an average of around 90MPG US, or 108MPG IMP on my Rebel, riding it lightly.