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

alvaro84 · 03-22-2014, 03:37 AM

Well... I hope someone will pop up to answer your questions, I only have some experience with the same engine in a different model. The F650CS I own (look for the bike named Teresa in fuel logs, right below my avatar) is like a lowered, street-oriented version of your son's bike. The seat is 9cm (3.5") lower (so much for the wheel travel) there's no beak and there's a belt drive instead of chain. But the engine, and the frame is the same, so possibly my experience still apply somewhat.

I'd say these changes make FE a bit better, but nothing stellar, so you'd need something more serious. Yes, you can see 80-90mpg tanks in my logs, even a few over 90, but those are not at 70-75mph, more like 50. I tried different angle setting on the windscreen (with a home brew little gadget from an f650.com mate), but that didn't change anything either, I could only make things worse. A more complete fairing would probably help. Or an aerotrunk, low&slow seems to get good results with it: http://ecomodder.com/forum/showthrea...ect-27216.html

It might be the best option because large, protruding side fairings are the best way to make a bike useless on the trail where you'll fall and get up a lot, and break the expensive plastic in the process.

If you plan to keep cruising at 70-75 mph, taller gearing might help too. Teresa revs 4000 at indicated 100km/h (62mph) and I'm absolutely sure she could easily handle 70+ mph at that range if I could change the gearing. You have chain drive so it's way easier for you. It might qualify as compromising off-road function too, though. And it might be a drawback FE-wise in the city too, as you'd probably have to use a lower gear - I'm at the very bottom of 4th at 50-something indicated km/h (30-something indicated mph).

Shaving off that weight won't help FE too much (possibly you won't be able to measure the difference at all), but it can surely help handling and won't make anything worse, so why not. Except for removing ABS, that helped me out a few times. Might be bad off the road, though, so it's your choice again.

03-22-2014, 03:37 AM	#2 (permalink)
alvaro84 Master EcoModder Join Date: Jul 2010 Location: Fehérvárcsurgó, Hungary Posts: 384 Teresa - '04 BMW F650CS Motorcycle 90 day: 80.53 mpg (US) The YARDIS - '99 Toyota Yaris 1.0 90 day: 59.52 mpg (US) Thanks: 4 Thanked 11 Times in 10 Posts	Well... I hope someone will pop up to answer your questions, I only have some experience with the same engine in a different model. The F650CS I own (look for the bike named Teresa in fuel logs, right below my avatar) is like a lowered, street-oriented version of your son's bike. The seat is 9cm (3.5") lower (so much for the wheel travel) there's no beak and there's a belt drive instead of chain. But the engine, and the frame is the same, so possibly my experience still apply somewhat. I'd say these changes make FE a bit better, but nothing stellar, so you'd need something more serious. Yes, you can see 80-90mpg tanks in my logs, even a few over 90, but those are not at 70-75mph, more like 50. I tried different angle setting on the windscreen (with a home brew little gadget from an f650.com mate), but that didn't change anything either, I could only make things worse. A more complete fairing would probably help. Or an aerotrunk, low&slow seems to get good results with it: http://ecomodder.com/forum/showthrea...ect-27216.html It might be the best option because large, protruding side fairings are the best way to make a bike useless on the trail where you'll fall and get up a lot, and break the expensive plastic in the process. If you plan to keep cruising at 70-75 mph, taller gearing might help too. Teresa revs 4000 at indicated 100km/h (62mph) and I'm absolutely sure she could easily handle 70+ mph at that range if I could change the gearing. You have chain drive so it's way easier for you. It might qualify as compromising off-road function too, though. And it might be a drawback FE-wise in the city too, as you'd probably have to use a lower gear - I'm at the very bottom of 4th at 50-something indicated km/h (30-something indicated mph). Shaving off that weight won't help FE too much (possibly you won't be able to measure the difference at all), but it can surely help handling and won't make anything worse, so why not. Except for removing ABS, that helped me out a few times. Might be bad off the road, though, so it's your choice again.