[ProDigit]

I have done some testing with my CBR300R for better fuel economy.
It turns out that the bike is best tuned stock, and changing the gearing from 14t front sprocket, 36t rear, to a 15t front, 34t rear.
Note, not all 34t sprockets fit the rear. The chain can cut over the sprocket bolt at 34t.

The CBR300R has quite a restrictive exhaust system.
Equipping it with a freeflow exhaust, does open up the engine to rev freely from 1500RPM onwards, as opposed to 4000RPM with the restrictive stock exhaust.

But aside from that, without fuel controller, there is no easy way to increase fuel supply to the bike, as the bike starts running very lean, and loss of power is noted.

So the best fuel ratios are gotten with the stock exhaust.
The gearing did help me get just over 310 miles on a tank (3.5Gal) of fuel; or get a MPG of 87MPG on the bike.
Mostly keeping it pinned at 40-50MPH.

While the CBR definitely did not beat any MPG records, to do just over 300 miles on $8 on gas is astounding!



The open exhaust system does give an increase in fuel mileage above 7.5k RPM; and the bike revs more easily to 9.5k RPM.
I think the open exhaust helped raising the HP curve from ~27.1HP at 8.5k RPM to about 28.5HP at 9k RPM, at the cost of mid rpm acceleration or torque.
I would just keep it all stock.