[mrstarr]

I have a 1987 Honda Rebel, that gets about the same gas mileage, and I know my gas mileage varies WIDELY depending on (1) the air temperature (2) the speed I drive (assuming constant) and (3) the weight on the bike. Depending on the time of year and how fast I drive, it can be as low as 50, or as high as 90+, on a bike I've loaded up with accessories.

I may be incorrect, but the hotter gasoline is, the more efficiently and thus explosively it combusts. You're going to get your best gas mileage in the hottest time of summer, and worst in the cold of winter. On the other hand, colder air is denser, containing more oxygen, however, it also means the air is more dense outside the engine too, leading to higher air resistance.

In your measurements, air temperature was not kept a constant.

Further, the slower you drive, the higher your MPG will be. At 85, your MPG will be horrid. Drive at moped speeds of 35, however, and you will see some awesome numbers. Indeed, mopeds regularly get over 100mpg without trying, simply because they only go 30mph and are extremely light.


Adding heavier tires does not seem like it would raise the MPG... the converse is true. You should be trying to shed as much needless weight as possible. The less you have to move, the higher your mpg.

Gearing up the sprocket, which I have done on my bike as well, may add a few mpg depending if the speed you are driving is at a gear just where the bike is lugging along in the highest possible gear, where you are making every explosive vapor of gas work the hardest to push the bike along and maintain its speed.

In other words, as an example, you're in 5th gear, driving at 35 mph, and the weight and pressure of moving the bike is pushing hard against every little combustion explosion, like a mule grunting and straining hard to pull a heavy load forward.


At any rate, you need to redo your tests where (1) temperature is a constant, and you list that constant (2) speed is a constant, and you list that constant, and of course (3) weight is a constant. And then make your charts, where you vary all of those but only one at a time, and chart how much each impacts your miles per gallon. I would start by keeping temperature and weight constant, and charting at the different speed ranges. Then next test, I would for each speed range, chart where the speed stays constant, but the temperature changes.

Weight... pretty obvious what that will do... less is more... but on say 500 pound bike, how much will taking 10% off add... 20%... and so on...