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Old 02-16-2009, 08:16 AM   #1 (permalink)
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Wr250x

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.


Last edited by derangedhermit; 02-16-2009 at 08:23 AM..
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Old 02-16-2009, 09:04 AM   #2 (permalink)
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if you use synthetic oil make sure that you use a wet clutch compatible engine oil or you will have to replace your entire clutch, amsoil makes a motorcycle oil that I use and like.
I haven't been able to find anything wrong with foam air filters, they are high flow, you can wash them and they catch more dirt they any other filter I've used.
touring tires, they tend to be good wet/dry weather tires, they wear for a long time and if you can find some that are made out of silica rubber then they should be lower rolling resistance without sacrificing traction.
An o-ring chain is going to last forever but it's also going to weigh the most, a good non o-ring chain with chain wax or bo-shield on it should last a number of years.
as for a faring, the rear of you is the least aerodynamic part, so building up your seat behind you will help, wearing a small back pack, having a fearing that helps to keep the air flow attached behind your legs, removing the rear fender/license plate holder, dropping your handle bars a few inches so your whole body is dropped.
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Old 02-16-2009, 09:24 AM   #3 (permalink)
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First aero, then gearing (since you won't need the same power to cruise at speed).

Ryland's right: don't forget about the rear. I take it you've seen some of the other project bike threads here (like the electric aero Ninja 250 and the fairing/gearing project going on with the Suzuki Burgman).

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Old 02-16-2009, 04:05 PM   #4 (permalink)
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When you start with aerodynamic mod's you will find out that at higher speeds more power is left to do acceleration. This means that you can use an higher gearing and lower the rev's and fuel consumption. A manual six gearbox is ideal for that. An other thing to address is the engine temperature. I have problems on my Suzuki Burgman to get the temperature in the cooling water after reducing the air resistance. I already reduced the air to the radiator with 50%.
I am very interested in your project.
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Old 02-16-2009, 05:40 PM   #5 (permalink)
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Quote:
Originally Posted by MetroMPG View Post
First aero, then gearing (since you won't need the same power to cruise at speed).

[...]I take it you've seen some of the other project bike threads here (like the electric aero Ninja 250 and the fairing/gearing project going on with the Suzuki Bergman).

Welcome to EcoModder.
Thanks, MetroMPG. Yes, I have looked at those two projects. I think I will trade leaning forward to get ultimate mpg instead of a tall tail structure ala Craig Vetter. I worry about crosswinds. I also worry about aero stability, more of an issue for two wheeled vehicles. I'd rather have the drag back and the CG forward, like an arrow or a rocket. That doesn't mean it can't be cleaned up back there, though. That's the best real storage space on a motorcycle, so I hope to use behind the legs and back for compact practical storage that sort of "fills the hole in the air".

Quote:
Originally Posted by janvos39 View Post
When you start with aerodynamic mod's you will find out that at higher speeds more power is left to do acceleration. This means that you can use an higher gearing and lower the rev's and fuel consumption. A manual six gearbox is ideal for that. An other thing to address is the engine temperature. I have problems on my Suzuki Burgman to get the temperature in the cooling water after reducing the air resistance. I already reduced the air to the radiator with 50%.
I am very interested in your project.
Are there any "rules of thumb" for best gearing for cruising mpg? I think I read here that somewhere below the max torque rpm is best, but where? As far down in rpm as the engine will still maintain speed?

Do you mean your Burgman engine has trouble reaching (or staying in) normal operating temperature range? The WR250X cooling system has a thermostat, so flow through the radiator is (mostly) shut off if the engine is cool.

Ryland:
Synthetic: Yes, I plan to move to the Yamaha-approved synthetic.
Foam air filter: check (stock is foam)
Lower handlebars: Good idea. So far I have shortened them by 2" (from 30.5" to 28.5") to reduce frontal area a bit. I will have to see what it feels like with lower bars.
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Old 02-18-2009, 10:06 AM   #6 (permalink)
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[/QUOTE]Lower handlebars: Good idea. So far I have shortened them by 2" (from 30.5" to 28.5") to reduce frontal area a bit. I will have to see what it feels like with lower bars.[/QUOTE]

You may be able to use your stock bar for this. Remove everything, flip the bar end over end so that the rise now lowers the handgrip surface. Check for clearance to the tank at full lock steering.
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Old 02-20-2009, 10:23 AM   #7 (permalink)
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I flipped the bars to give it a try. It gave about a 6 inch drop from where they were. I might also try a set of straight bars. I can bend bars out of EMT for testing, that will be fun.

Hmmm, bars you could set high for slow speed riding and then swing to "dropped" position for highway riding would seem ideal.

I already have 17" and 21" front laced wheels I can swap out, and 17" and 18" rear wheels. I can also have a 19" front made, if I like. The 21" front raises the front of the motorcycle by 2".

I'm thinking that I want:

- low rotating wheel mass for starts and stops (low rim, tire, and tube weight)
- low rolling resistance
- reduce frontal area (low chassis and narrow tires)
- reduce drag of the front wheel somehow (partial "pizza pan"? wheel fairing/fender?). I guess the rear doesn't matter as much, but I don't know.

It would point toward 17", or at most 19", front wheel. At the rear, it seems like 17" would be better, because the rider would sit a little lower.

Does all this seem like the right direction?

Does anybody know if radial tires on motorcycles tend to have lower rolling resistance than bias ply?

I need some accurate way to measure fuel usage. Motorycles don't have OBD-II. Mine is fuel injected. Does the mpguino measure injector pulse width * pulses, and given injector data, display how much fuel is used?
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Old 02-20-2009, 04:58 PM   #8 (permalink)
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Boy I dunno about spending too much time on aerodynamic improvements for the WR. If you spend time and money fitting smaller wheels I think it will be unlikely to make a noticeable difference. Changing the bars is a good effort and with EMT you can custom make 'em to your liking, not some off the shelf bend. I really like the adjustable bar idea!!!

If you're really looking for outstanding aero, start with a 250cc cruiser like a Suzuki GZ250, or Honda Nighthawk 250. These are already really low, can be fitted with skinny tires and the gearing adjusted. Adapt/create a slippery fairing on these and it seems that 90+mpg should be reasonable.

For the cool WR, play with gearing to complement your riding style. Go as tall as reasonable, downshifting for a sizeable hill on the freeway is no big deal. Maybe a small windshield to slip some air around your torso. The 100 mpg target is only really possible with good hypermiling technique or truly outstanding aerodynamics. Since the WR is set up for hooligan fun, not aero, just enhance it with minor mods and good riding technique. You'll be getting more smiles per gallon than anyone.
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Old 02-20-2009, 08:56 PM   #9 (permalink)
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you should be able to get clip on handle bar (crotch rocket style that clamp on the forks) they are lighter and lower then normal dirt bike handle bars.
If you cover the wheels I would just cover the rear as covering the front is going to make it handle like it has a sail on the front, a cross wind might get you killed, and as it is the spoked wheels are like egg beaters of course they are going to be better then wide flat blades hitting the air dead on.
I assume it has alloy rims, if not look in to those, they are pricey.
I changed my front sprocket on my Honda cb125 to a tooth larger and it made a world of difference and was around $15 and took minutes to change so if you can i would say order up a handful of sizes to try.
narrower tires are going to be lighter but I tend to go with good tubes over thin tubes as you only have two tires.
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Old 06-17-2009, 01:03 AM   #10 (permalink)
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Yeah-I know I'm responding to 4 month old posts!

Quote:
Originally Posted by derangedhermit View Post
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.
I too have an '09 wr250x and my FE jumped from 62mpg to 72mpg when I started running without the airbox side cover! I had no other changes made and the bike was totally stock. I thought it was just 'cause it was new and breaking in so I put the cover back on and to my surprise the mileage went back down around 62. I went to a 48t rear sprocket for some low end grunt but the mileage dropped to 57ish. I put a 14t up front (with the 48t still on back) which should be a ratio somewhere between stock and where I am now and if it doesn't get much better, I'm going back to the stock 42t rear.

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