80-100mpg hiway bikes? (travel speed/overstressed engines)

[bschloop]

I still think an aeromodded 250 would be enough for highway. for example, last year I rode from Michigan to Kentucky on my SR185 with a passenger and our luggage. we rode 60-65 mph most of the way, and got 85mpg. on the way home my passenger opted to go in the car with my folks, and I rode home @ 70-75mph, and still got 85mpg. My bike has about half the power of a ninja or CBR250. I could see either of those bikes doing even better in these conditions.

[sendler]

Yes. Full streamlining will raise the performance of a Ninja250 or CBR250R to let any 6'6 guy ride around at 100 mph if he wants. I wonder what the top speed of Alan's Vetter style Ninja is with the long gearing he has on it? 120 mph?
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[renault_megane_dci]

What I said previously, a marginally modded 250 will do 85 mpg and top out around 80 mph.
If streamlined to some extend, it can go faster and make more mpg at lower speeds.

It's never gonna be a useful towing vehicle thought ...

[bschloop]

I would consider even partial streamlining for 75mph 80mpg. a tail/trunk that matches the size and profile of the front of the bike, and tapers to a point at the rear would reduce drag without adding frontal area. smoothing over/ removing protrusions, vents, and such can help too, but one must figure out which ones are necessary, and which are just eye candy. if the typical width of a sport bike fairing were 18" then a tail would only need to extent 3' behind the rider's hips to follow the template, and come to a complete point.

[sendler]

True gps top speed for a stock Ninja250 seems to be about 99. I haven't ever topped mine out though. The new Ninja300 has videos of gps 110 mph runs. I have done top speed runs on my CBR250R. With the stock gearing, most really clean people get about 92 mph. With my 15% longer gearing I can see 96. Big guys that refuse to tuck have trouble getting past 80 mph.

[stillsearching]

Well the one thing I cant do is a full racing tuck, hurts my wrists too much, so that limits me to the ninja 250, standards, and cruisers. I just dont have alot of confidence about my ability to aeromod a cycle is all.

The main point of my post (which I don't know if I got answered at all yet :-/ not to gripe it's just to reiterate my question) is where the crossover points are as far as mileage at a given engine stress. I might be able to aeromod a 125cc then regear it for instance, but i'm still trying to find more detail about (for comparison) what unmodded speed the 125cc becomes less efficient than the less stressed 250cc. As near as I can tell the mileage for bikes is just a city cycle, and I keep reading bike tests of a small cc bike supposed to get 115mpg testing at 60mpg and similar so it's frustratingly hard to find real world numbers.

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What i'm really looking for is speed to mpg charts for any low CC bikes. There is a car thread here with people helpfully posting their results, showing some interesting variances between different cars. (including some that drop pretty drastically at faster speeds for instance) I'd love to see that for 50cc, 125cc, 250cc common motorcycles. Where is the 'knee' where it drops like a stone from overloading?

[sendler]

Originally Posted by stillsearching

Well the one thing I cant do is a full racing tuck, hurts my wrists too much,

I lay my chest on a tall tank bag stuffed full with a sweater. There is zero weight on my wrists and very little on my butt. This is very comfortable and the bike handles crosswinds like a dream with your torso anchored.

Originally Posted by stillsearching

so that limits me to the ninja 250, standards, and cruisers.

Which bike did you eliminate?

Originally Posted by stillsearching

real world numbers.

Fuelly has thousands of bikes logged and nearly every US models has at least a few listed. You can message a few people to ask them what their average speed is.

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Originally Posted by stillsearching

What i'm really looking for is speed to mpg charts for any low CC bikes. There is a car thread here with people helpfully posting their results, showing some interesting variances between different cars. (including some that drop pretty drastically at faster speeds for instance)

smaller engines more often operate in the high efficiency zone of 50%-90% load but gearing has to right to keep the rpm just below the first torque peak. Gearing is easy with bikes.

Originally Posted by stillsearching

I'd love to see that for 50cc, 125cc, 250cc common motorcycles. Where is the 'knee' where it drops like a stone from overloading?

A drop off in efficiency may happen above 90% load where the fuel injection selects a richer map to avoid pre detonation. Below full load, speed vs fuel consumption is more a matter of aerodynamics and rpm.
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Forget 50cc scooters. You will never keep up with rush hour traffic on a 40 mph boulevard and become a hazard. A 125 scooter is very useful up to 50 mph if you never need to go on the super highway, and can get 90 mpg at that speed. My PCX150 will run 55 mph all day long and bring back 90 mpg.
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A Honda rebel has small cruiser ergos and can get 70 mpg at 50 mph but will struggle on the highway. A Suzuki TU250 is a comfortable city bike that can get 80 mpg and is fuel injected but is on the edge of adequate performance on the highway. A Ninja can get 75 mpg at 50 mph with a big gearing change and easily run 90 mph on the highway. The CBR250R is my choice for highway commuting where most people get 70 mpgUS (I am over 90 mpg in a tuck and with some following) at 65 mph and can get 85 mpg at 50 mph on a slow back country tour.
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I won't consider any carbureted bike now that the CBR250R, TU, Ninja300 and the PCX125/ 150 are injected. I can't wait to trade my 09 Ninja for the new model as it is very cold blooded.