[redyaris]

Originally Posted by derangedhermit

First post, glad to be here.

I have a Yamaha WR250X - factory pics here.2009 Yamaha WR250X Gallery

It has a water cooled fuel injected 250cc engine. 6-speed manual transmission.

It gets around 60 mpg stock. I would like it to get 100 mpg when cruising in 6th. It seems to me the main area to address is CdA. I was thinking of:
- lowering it by reducing the suspension travel and ground clearance from 10" to 7" or so
- putting on a fairing, something like the Can-Am 125cc fairing at LANDSPEED, LAND SPEED RACING, SALT RACER, BONNEVILLE, EL MIRAGE, FAIRING, SEAT, FENDER, SCTA, but with lights, and with mirrors behind the fairing
- doing some fuel tuning with a Power Commander (although I doubt there is much to be gained)

The exhaust has a catalytic convertor, but no lambda sensor.

I'm not sure what changes are most effective on motorcycles. (I have been to Vetter's web site). Maybe:
- Cover the rear (laced spoke) wheel with dish covers
- Make sure there is no brake drag
- Bearing grease and engine/transmission oil - how much difference can this make?
- Gearing - it is easy to change the final drive ratio by changing sprockets. What would I shoot for?
- What else?

EDIT: What I would really like for the fairing is to make it out of a stretch fabric, like BMW did on one of their concept cars.

To start with I have a WR250R with the bigger wheels 21' front and 18' rear. The R is undderpowered in top gear and therefore a good candidate for aeromodding. I have a 14T front sprocket but have not put it on yet because until the aero is better ther is no point yet. I started by making a long skid plate from only 2" behind the front wheel too 2" infront of the rear wheel. This winter I am making aluminium cargo boxes to fit close behind the riders legs and making a front fairing that is better than stock. I believe this type of bike can be made more aero but is not the best choise for that type of project. I still want to ride this bike in the dirt and on the gravel roads. The fuel tank is so small 7.5L that better fuel economy would be real benificial.