My 2005, 883, best mileage was 57 mpg, solo, running 55-60 mph. If I ran 70-75 mph I'd drop to ~50. I changed the front pulley to a 32 tooth and now I can get 60 mpg+ riding at 70 mph, all day long. Town mileage is about the same, 48-50.

 

32 tooth sprocket? How is your low end take off now? I find keeping the rpm range 3000-3500 when riding around town compared to lower might get me a gallon or two better milage. always get better running for awhile on the interstate. I'm always some where between 40-50 mpg.

 

An engine operating alone, not propelling a vehicle, has the best brake specific fuel consumption (units of fuel used per units of power produced) when running at 3/4-7/8 throttle for any given RPM. The engine does best around its torque peak, but the total variance of BSFC depends MUCH more on throttle opening than on RPM.

This is because of two things. First, the wider the throttle is open, the fewer "pumping losses" the engine experiences. Pumping losses refer to the "wasted" power necessary for the engine to suck air past the throttle butterfly. Ordinarily, this would mean that WOT is best, but that brings us to the second reason: EFI systems and even carburetors are designed to operate slightly rich at full throttle, so WOT actually has a brake specific fuel consumption penalty in practice.

In terms of total fuel used over time, however, RPM is always the 800-pound gorilla.

Now, that's just the engine operating alone. Things get different when you start working with gearing and wind resistance and the nature of the road (e.g. more/less friction between the tire and the road, uphill, downhill, etc). Motorcycles (well, cruisers like our Harleys anyway), despite their small size, are not at all aerodynamic. This means that drag plays a huge role in mpg returned by a bike and higher speeds will really kill mileage.

Putting all this together though generally results in the best steady-state fuel economy happening when the bike is running at relatively low RPM in top gear. For an '08 Sporty 1200 that means something like 50 mph in 5th. It's a lower RPM (lower fuel use over time) with a larger throttle opening (lower fuel use per unit of power produced) but still not lugging and it's keeping drag low.

Of course, not all riding is steady-state riding and there are more and less efficient ways to accelerate as well. Again, using the knowledge of highest brake specific fuel efficiency it turns out that the most efficient way to accelerate is to use a lot of throttle, but to shift relatively early. In other words, something like 3/4 throttle while upshifting at 3,500 RPM. Even waiting until 4,500 or 5,000 RPM with 3/4 throttle can yield more efficient acceleration than just puttering away from a stop with smaller throttle openings.

 

+1 to that, ain't it great!

By the way:
The average response time of a 911 call is over 3 minutes....
the average response time of a .44 magnum is 2.3 seconds...

Your call, 911 or Winchester

The FBI, CIA, fire department, ARMY, NAVY, MARINES don't call 911.

FYI

 

Which makes me wonder how, what we add or remove from our bikes affect drag. For example. Does my clip on windshield add or remove wind resistance. What about seemingly cosmetic things like headlight visors and chin spoilers?

 

Looking at my car 14mpg on city, anything above 30mpg looks like Christmas to me

 

Hmmm. Just went through my first tank using just over 3 gallons and only got 38mpg on my 07 Sportster. About 80% highway.

 

I was disappointed with the mileage of my '08, too. It was about 43 mpg highway.

 

Most riders on sportsters put super loud exhaust on them and try way too hard to sound like their big twin cousins by lugging the crap out of their sportster as they cruise around. It destoys mileage For the cool image.

Best rpm to cruise around on with these engines is 2900 rpm-3500 rpm. Not shifting rpm but running the streets rpm. For an 883 at 40 mph that means running around in 3rd gear for a steady cruise at that speed. Oil temps will be down too.

Running twisties I get 55-58. Super slab 65-70mph I get 63 without throw over saddle bags and 58 with. Switched to a bungee corded alice pack behind me and mileage returned. Running faster than 70 reduces mileage. A 100 mile run at 90mph gets me 48~mpg.

In the end it all depends on how much extra heavy chrome you bolt on, tire psi, fattness of the rider. I come in at 164# and run psi tire maker says to on my bike checked weekly.

In the city its 44-45mpg steady and in the winter when I warm it up before rides its 38~mpg.

 

The carbureted models got better mileage "out of the box" than the EFI ones that followed.