Fuel Economy, Hypermiling, EcoModding News and Forum - EcoModder.com - View Single Post - Aero mods to dual sport or dirt bike, fully retaining off-road function

Otto · 03-22-2014, 02:57 AM

My son just bought a BMW F650GS Dakar dual sport motorcycle:

https://encrypted-tbn0.gstatic.com/i...Wek6CGEtSrfJrs

http://www.sierrabmwonline.com/image...indssplate.jpg

This single cylinder 4 valve thumper gets ~63 mpg cruising at 70-75 mph on the highway, which is excellent, due to fuel injection, decent gearing, etc. It's 50 hp engine and fuel economy is as good as otherwise similar bikes with much less displacement and power, i.e. similar to ~400cc bikes with ~35 hp, despite terrible aerodynamics typical of motorcycles. OTOH, it's a target-rich environment.

Notice the beak, basically unfaired frame, fork, etc.

The beak is basically useless from a functional standpoint, and draggy. The front wheel and fork is an aero abortion. The windscreen is cosmetic and causes annoying buffeting at speed.

This bike weighs ~390 lbs. dry/empty. By stripping off the useless crap like the beak, replacing the battery with a smaller/lighter one, dumping the effectively worthless ABS, etc. some owners have reduced the bike to ~340 lbs. dry/empty, thereby improving acceleration, handling, and fuel economy.

Question: What lightweight aero mods can be made which would improve ~75mph highway cruise fuel economy, yet not compromise off-road handling, ability to cross shallow streams, etc.?

I'd bet that ~100 mpg is well within reach, while retaining off-road function in conventional upright riding position.

How best to do it? I have some ideas including a lightweight fairing, but would like to get your perspective.

03-22-2014, 02:57 AM	#1 (permalink)
Otto Master EcoModder Join Date: Mar 2008 Location: USA Posts: 568 Thanks: 1 Thanked 73 Times in 58 Posts	Aero mods to dual sport or dirt bike, fully retaining off-road function My son just bought a BMW F650GS Dakar dual sport motorcycle: https://encrypted-tbn0.gstatic.com/i...Wek6CGEtSrfJrs http://www.sierrabmwonline.com/image...indssplate.jpg This single cylinder 4 valve thumper gets ~63 mpg cruising at 70-75 mph on the highway, which is excellent, due to fuel injection, decent gearing, etc. It's 50 hp engine and fuel economy is as good as otherwise similar bikes with much less displacement and power, i.e. similar to ~400cc bikes with ~35 hp, despite terrible aerodynamics typical of motorcycles. OTOH, it's a target-rich environment. Notice the beak, basically unfaired frame, fork, etc. The beak is basically useless from a functional standpoint, and draggy. The front wheel and fork is an aero abortion. The windscreen is cosmetic and causes annoying buffeting at speed. This bike weighs ~390 lbs. dry/empty. By stripping off the useless crap like the beak, replacing the battery with a smaller/lighter one, dumping the effectively worthless ABS, etc. some owners have reduced the bike to ~340 lbs. dry/empty, thereby improving acceleration, handling, and fuel economy. Question: What lightweight aero mods can be made which would improve ~75mph highway cruise fuel economy, yet not compromise off-road handling, ability to cross shallow streams, etc.? I'd bet that ~100 mpg is well within reach, while retaining off-road function in conventional upright riding position. How best to do it? I have some ideas including a lightweight fairing, but would like to get your perspective. Last edited by Otto; 03-22-2014 at 03:17 AM..