Pretty ridiculous that the big 650s get nearly the same mpg as our featherlight 250s. Plus, they have larger fuel tanks.

I have a 90 mile each way trip planned on Saturday and I don't want to run out.

I've foudn that I hit reserve with much more than 0.5 gallons remaining. I have stalled out, grabbed reserve, and then filled up 10 miles later and only needed 1.3 gallons.

 

I can go about 250 miles give or take on a tank on the KLR.

 

my klx cuts out at 90 miles, so im getting 60 mpg. doesnt matter if im on the freeway or in town it always cuts out within 1 mile of 90 miles

 

In 2008, Top Gear ran the now-classic comparison of fuel economy between a Prius & an M3. On the track, the M3 got 19mpg while the Prius only got 17mpg illustrating that smaller engines aren’t particularly efficient when they are tapped out. Same is true of our little KLXs…

 

Then there's the theory that a gasoline engine is most efficient at WOT since there is no throttle plate causing pumping losses. I think the high RPMs required for freeway speed is where the poor mpg comes from.

Then there's the thought that all bikes weigh about the same, all have terrible aerodynamics, so it takes a certain amount of fuel to get the bike down the road whether the engine is a 650 or a 250.

 

Is the odometer correct on the SF ? I've read the speedo was off 10%.

Reason I ask is I went 110 miles on last 3 tanks (1.5 Gallons) before hitting reserve.

73.3 mpg, riding rural roads. 45mph Speed Limit.

2009, 250SF, Dyno Jet kit and FMF

 

It depends upon what efficiency is being measured. If we're measuring the work produced by the engine, I can see how WOT might produce more work per unit of fuel burned. Maybe. This kind of measurement of efficiency has a lot to do with workload/heat generation. Again, I'm not sure of the calculations, but, it's a different kind of efficiency than Miles Per Gallon.

But, when you put the engine in the real world, you have stealers of work such as chain drag, bearing drag, tire slippage, and a giant one is air resistance. If you are a bicycle racer, you know that at about 15 mph, air resistance starts to make a difference in how much work it takes to maintain speed. And I believe the resistance is cubed in relation to speed, so, yep, air resistance is a biggee.

 

I'm about that too. It was slightly better before the TBR exhaust and rejet but it hasn't dropped much since. I'm very happy with the results.

I average about 55-60 mpg per fill up. I have just over 1,000 miles on my SF.

 

The trick is to get WOT while at lower rpms, at peak efficiency rpm, which is not freeway speed rpms on our KLX. This is tough to do but the guys have accomplished it with varible pitch props on airplanes and realized huge fuel savings.

Lower rpms generally get better mpg anyway. This is why trucks have hauling gears like 4.10 or they have highway gears like 3.08s in the rear end. Better mpg with the lower gears (lower cruise rpms) so long as you have enough power to make it.

Maybe the 15 or 16 tooth CS sprockets result in better mpg due to lower rpms and a more open throttle plate.

 

ya same here, but i have 16,200 miles lol