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Old 12-06-2011, 05:19 PM   #1 (permalink)
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Buying a bike for MPG/Vetter Challenge, what would be your favorite?

One of the issues for the Vetter Challenge that is being discussed in various places is deciding which platform, or donor bike to use. Some people want to use thier existing bike, some want to get the "best", some want the cheapest and most common. This whole bike choice thing will probably never be resolved completely as the optimum existing bike doesn't exist to suit everyone. We only have what is out there now to choose from. The best we can do is get one that is good enough for our purposes, or slightly modify one towards optimizing it for the purpose of high MPG.

The important technical factors in choosing a donor bike appear, in no particular order, to me to be:
  • Highly efficient motor, about 250cc seems good, some are better than others.
  • Chain drive, ability to change gearing, and chains are more efficient than CVT and shaft drive.
  • Low seat height, reduces frontal area and corresponding total drag. IIRC 24" is the lowest legal height in most states, though I've NEVER heard of someone being ticketed for too low of a seat.
  • Air or water cooling. Water cooling allows higher compression ratios and being able to place radiators where you want them among other things. Air cooled are simple, non-toxic and noisier.
There are also non-technical and practical factors like:
  • Common availability. Hard to find out of production bikes may fit the bill, but only for the select few that can find them.
  • Cost. This threshold varies from person to person.
  • Ease of modification. Some bikes will be easier to modify than others for mpg and aerodynamic goals.
  • Chinese. Some don't want to send money to them, some don't care, some question thier reliability. It's up to you. Darn inexpensive, if you wrench your own rides.
Craig is thoughtfully trying to design something that could be used on many different motorcycles. The Vetter streamliner front fairing blocks alot of wind so water cooling with this would probably be needed.

Alan's Ninjette with only the Vetter tail actually gets better mpg than Craigs fully streamlined Helix. Whether this is due to a more efficient engine and/or drivetrain or some other factor hasn't been dithered out yet. It does demonstrate however, that an un-optimized front fairing can still work with a good tail section. This discovery may open up some choices to include an efficient air cooled engine with a minimal front fairing and a tail, as I see it.

Below is a list of some of the more common freeway-capable bike choices and salient features that have been posting 80+ mpg figures. It's not a complete list as you all will have additions, I'm quite sure.

  • Kawasaki Ninja 250 (1986 through '07 are best). Very efficient water cooled motor, very common, very cheap, changeable gearing. High strung motor not optimized for low speed operation, higher than optimal seat height, cramped sportbike leg position for some.
  • Honda Helix 250. Pro: Craigs paved the way! Average motor efficiency, water cooled, super easy to ride, common, cheap, changeable gearing available through only one source, low seat height, comfortable, Chinese copies still made. Tiny 10" wheels, inefficient CVT transmission.
  • Honda NX250. '88-'89 I think, very efficient water cooled motor, changeable gearing, comfortable upright seating. Hard to find, high seat height, hard to find, doesn't have common street tire sizes, hard to find.
  • CBR250R. Since 2011, very efficient low friction water cooled motor designed for mid range, feedback fuel injection, changeable gearing. New, expensive (relatively), few in resale yet, high seat height.
  • Yamaha V-Star/Virago 250: Since 1988, Very efficient long stroke air cooled motor, common, cheap, changeable gearing, tolerates taller gearing well, comfortable low cruiser seating, Chinese clones are cheap. It's air cooled.
  • Honda Rebel 250: Since 1986, Efficient air cooled motor, common, cheap, changeable gearing, comfortable low cruiser seating, most cramped small cruiser. It's air cooled.
  • Suzuki DR200/Honda CRF230/Yamaha XT225/TW200/Chinese 200 dual-sports and Motards: Lumping these together as they are very close in performance and mpg results. Efficient air cooled motor, common, cheap to very cheap, changeable gearing, comfortable upright seating, torquey durable motors. Tall seat height, 15-17hp is JUST BARELY enough without aerodynamics, air cooled motor.

What is your favorite among these?

Keeping the availability, cost, practicality issues in mind, can anyone think of a better bike platform for the Vetter challenge other than these? If so, please post.

-Garth

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Last edited by MetroMPG; 12-23-2011 at 08:16 PM.. Reason: added some formatting - hope you don't mind!
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Old 12-06-2011, 06:40 PM   #2 (permalink)
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Ninja 250, install better exhaust, flatside carbs (Keihin FCR) small pod air filters, taller gearing, streamline it, have it dyno jetted. Should be extremely easy to hit 100 mpg.

At least, this is my bike, and mods of choice when done modding the car.
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Old 12-06-2011, 07:02 PM   #3 (permalink)
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A member here posted a 90 MPG highway mileage on his 2011 CBR250R with a 15 tooth front sprocket and a tuck on his daily commute. I think that is at something like 62 MPH average speed. There are some salvage rebuilds coming into the market for $2600.

The basic CBR with modern fuel injection and feedback fuel system is supposedly about 10 MPG better than the Ninja, but you can find cheap Ninjas just about anywhere.

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Old 12-06-2011, 08:25 PM   #4 (permalink)
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The Ninja 250 is the bike that fits the critera the best. price;/performance and modability.
The "problem" with aircooled bikes is the management of the cooling air. If the cooling air is managed they are fine. Good management of cooling air requires ducting to and from the cylinder and head.
The next best choice would be a single cyclinder duel sport bike motor from 200 to 400cc. Look for something that has a bolt on rear subframe; if they are available on none racing type dirt bikes, that can be replaced with a rear subframe with a lower seat height.
The nice thing about the 250cc V-twin bikes is they start with a low seat height. An other consideration is; can the stock handle bars be easily replaced with narrower ones for better aero.
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Old 12-06-2011, 10:55 PM   #5 (permalink)
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Garth, Excellent post!!! I think your list is pretty comprehensive. I think the Honda CBR 250 would be the best choice if price were no object or as time passes and they become more available through the used and salvage markets. But since cost and availablity is a major factor for people like myself I will probably end up with a Ninja. On CL, Ninja 250s outnumber the other leading candidates by probably 10 to 1 at least.
Even though I've looked only at Ninja 250s so far , I am stilled intrigued by the Virago 250's better low-end torque , lower seat height and better fuel economy in stock form. The only issue would be getting adequate cooling with streamlining in place. Alan Smith had big problems with his Honda 230 before switching to a Ninja 250. I wonder if you couldn't leave the engine exposed and still get great FE or design in efficient cooling ducting or an electric fan.
I started looking last week for my future Vetter Challenge bike and hopefully will find a good candidate soon.
Garth, Thanks again for all your great work during the Las Vegas to Barstow Vetter Challenge, it was great to meet and spend time with you.
all the best , Vic
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Old 12-06-2011, 11:11 PM   #6 (permalink)
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I'm starting to look for a Ninjette.

Kawasaki also used the same engine in the 250 eliminator. It was a cruiser style. Just did a search of allofcraigslist.com and only came up with one.

A company called ecotron offers a fuel injection set up w/a tunable ecu for the 250 Ninja. I wonder if an Mpguino could be set up to read it.

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Old 12-07-2011, 09:32 AM   #7 (permalink)
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That is a pretty decent list IMO.

The Ninja 250 is the clear winner when price is a factor. The engine has proven to be pretty efficient, even though it makes its peak power and torque WAY up there.

As far as the Ninja mods BHarvey suggested - I have to disagree. I don't think you'd want to go that direction from a mileage perspective. From what I have heard about flat-slide carbs, they don't like small throttle opening. I would think you'd want to drop down in carb size to increase the velocity at smaller opening while sacrificing some (unneeded) top-end power. Pod filters would kill any positive intake pulses (and your throttle response and mid-range power). Ducting in warm air to the airbox would be better IMO. You want small exhaust pipe dia and some amount of backpressure, so I wouldn't mod the exhaust system.

The CBR250R would be better, but not very easy to get a cheap donor if you were planning to scrap most of the body work.

A 250cc single enduro might be a good choice. Most have 5-speeds and air cooling, but there are a few that would work. Since you would most likely be adding full custom body work, not having any to start with wouldn't be an issue. You would want to drop it down, but a KLX 250 has a lot going for it - water cooled, 6-speed, and F.I. Should run pretty well at lower RPMs when cruising with the addition of aero body work and tall gearing. Not many used to choose from I would expect, but I don't think they are very expensive used if you can find one.

EDIT: It looks like only the current standard model KLX (not the S or SF models) are F.I. Saw a couple 2010 models listed on CL in my area - both for around $4000. So they aren't really "cheap" I guess. Other than the NX models, I'm not sure how many other 250 Honda singles are water cooled.

The older Honda NX250 is water cooled and 6-speed as well, just obviously no F.I. I've seen them on CL occasionally.

Don't know much about the others, but from what has been proven in past competitions, water cooling is a requirement when going full-aero.


Jay

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Old 12-07-2011, 10:24 AM   #8 (permalink)
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BHarvey: Sounds like most of the mods you listed benefit max power production. The FCR is a great very tuneable carb no doubt, but I could only find a round slide kit, and those were 31mm listed as *Race Only* vs the stock 27mm. Not sure if there would be a FE benefit there vs tuning the stockers properly. The pod filters are great for top end, large air box volume is beneficial for low and mid range power torque production but there could be a reduced air flow friction benefit though. My GPz550 had pods, they were loud and didnít really help FE much if at all with Yosh pipe and a jet kit. For 90-100 mpg, the horsepower requirements are far less than what the Ninja 250 can easily make in stock form.

Old Mechanic: Good idea to look at salvage rebuilds! If the broken bodywork will be replaced or covered with a Vetter fairing anyway that is a cost that can be avoided. Iíd not buy one without personally inspecting the mechanical and structural parts though.

Redyaris: I know you are doing great things with the GS and Ascot. Larger motors turning slower can also return stellar mpg figures. The air-cooled direction I was hoping to address by the fact that Alans Ninja with the more or less stock front fairing is a lot like the stock air cooled GS. And it tops the gasoline powered FE list in the challenges. This supports the idea that an air cooled design could still work well.

Keep in mind that air still needs to be ducted to a water cooled engine radiator for it to cool the engine.

Vic: I just thought Iíd post this to try to get all the heads in the same place about bike selection. If the frame can be easily modified for a low seat, the Ninja is no doubt the obvious choice right now falling within most of the constraints weíve put on ourselves. Iím sure youíll find a suitable donor soon. Hope to meet up with you again, next time I expect to be riding.

FXSTi: Right on, the Eliminator is really hard to find and since nobody has mentioned it, just the rare NX, I didnít either. Other harder to find high MPG bikes that come to mind right now are the Kawasaki GPz305, CSR305, KZ440, Suzuki GN400, GN250, Yamaha SRX250, Honda XL250 1982+. The BMW 650 Rotax is quite fantastic as well I understand.
Wouldnít that be fantastic to have an Mpguino readout on the bike!

So far it looks like the Ninja 250 is the crowd favorite. Easy, cheap, works pretty well though not optimum.

For big-effort, maybe the optimum current bike would be a modified, lightly crash damaged CBR250R made into an Alligator wannabe, then streamlined? Not exactly easy but should produce an easy 120+ mpg under the Vetter conditions. Brushing up on aluminum welding skills would be a good idea for the frame and swing arm changes.

Anyone have other ideas for a good bike to start with?
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Old 12-07-2011, 12:13 PM   #9 (permalink)
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Quote:
Originally Posted by FXSTi View Post
I'm starting to look for a Ninjette.

Kawasaki also used the same engine in the 250 eliminator. It was a cruiser style. Just did a search of allofcraigslist.com and only came up with one.

A company called ecotron offers a fuel injection set up w/a tunable ecu for the 250 Ninja. I wonder if an Mpguino could be set up to read it.

Kirk
I was very surprised when I found 2 Kawasaki EL250's just within a few hundred miles of where I live. Especially this time of year. I hope someone can make use of one, if they're still available.


1988 Kawasaki Eliminator 250

2008 Kawasaki Eliminator
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Old 12-07-2011, 02:06 PM   #10 (permalink)
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Quote:
Originally Posted by Quasimoto View Post
I was very surprised when I found 2 Kawasaki EL250's just within a few hundred miles of where I live. Especially this time of year. I hope someone can make use of one, if they're still available.


1988 Kawasaki Eliminator 250

2008 Kawasaki Eliminator
Good catch. Those didn't show up on allofcraigslist.com. I must not have used the right search term. Does anyone know if the 2008 was revamped at the same time as the Ninja?

Kirk

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