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Motorcycle News, Editorials, Product Reviews and Bike Reviews

Readers Respond to “Diesel Motorcycles”

High gas prices here in the United States prompted our July 8, 2008 article regarding diesel motorcycles, and led to several email from readers. Here is what some of our readers had to say, both expert and non-expert, on diesel motorcycles:

  • I think it’s a dangerous thing for bikes to get too caught up in the
    whole “mileage, go green, save the environment” thing.
    We already get great mileage when compared to cars and by subjecting
    bikes to over scrutinization of the greenies and the government,
    could result in bikes that are less overall fun to ride.
    Be carefull what you wish for!

  • When I pulled up next to a rider on a classic BMW twin at a stop
    light awhile back, I commented that he had a nice bike. He looked at
    my 1998 Honda Pacific Coast and said something unflattering about its
    plastic bodywork, so I told him I was riding the latest engineering
    marvel, an electric/diesel hybrid. Of course no one is making
    anything like that these days, but I wish they would. My PC hauls me,
    my wife, and lots of our stuff in comfort, with enough performance to
    suit this old man, and I average more than 50 miles per gallon. But I
    believe bike companies should be doing far better than that. My
    friend with a Honda Gold Wing has a license plate frame that reads
    “40 mpg, one less car.” I’d feel a lot better if that number was 80
    mpg, or even higher. Motorcycle engineers should feel proud to have
    developed amazing machines with fantastic performance. But now, with
    rocketing gas prices and economic stress, it’s time for them to shift
    focus and start turning out functional vehicles with mileage figures
    that make sense for the world we all live in.

  • For my part, I ride a 2004 Kawasaki ZR-7S and a 2007 Suzuki DRZ400S. The first regularly delivers 60-65 mpg Canadian and the later
    gets about 70-75 mpg in the type of riding I do. It would be foolish to trade either in on a diesel just to pick up the extra 30 to 40 mpg,
    unless you are doing thousands of miles per year. However, when time comes to replace either, it would be nice to have a choice of
    gas or other. By then the products would be nicely sorted out for the late arrivals like myself.

  • Squarely from an mpg point of view, it would be a revealation to take a look at the small capacity ( 250cc and below ) motorcycles of East Asian Countries in general, and that of Thailand, Malasia, Vietnam, India or China in particular.

    Whether these may be Bobecks of in Thailand or commuter bikes of India, the one thing common is that, they have 100 cc to 200 cc single cylinder engines installed in them with most of them making do with 100 – 130 mm rubber rear footware. The general per capita income levels makes high fuel efficiency a necessity and traffic congested streets mandate an unwritten limit to the horse power requirements from these machines.

    As a result one can see upto 100 kml/ltr from the most economical 100cc machines to a more realistic 60 kml/ltr. That corresponds to 250+ miles per gallon for the former and 150 miles per gallon for the latter.

    chew on it….

  • i am looking forward to these. i frankly don’t understand why american companies are so slow to react to trends like fuel efficiency. especially if the tech is out there to be used. foreign manufacturers aren’t off the hook either. somebody bring one of these to market that is reliable, fairly lightweight (the diesel engine would likely not be made from aluminum although subaru has a turbo diesel in other markets that is all aluminum) versatile, and less than $12,000.

  • I for one would welcome a diesle (or petrol) motorcycle that can do 100+mpg. I think the requirements here in the UK are a bit different to the US. Here the journeys are (tend to be) shorter, so speed and comfort are perhaps not as important to us. My daily comute is about 20 miles round trip. However, petrol here is £1.20/Litre and diesel is £1.35/Litre! If they can give me a bike that can cruise happily at 70mph, is light – no more than 160 Kg, and does well over 100mpg (imperial gallon) then I would be happy. I’m almost describing a Honda CG125, but that’s a little on the small side (but still tempting).

    My wife has a VW Polo 1.4 diesel and manages 60mpg on the motorway. That’s impressive. A bike should be able to get *well* over 100mpg.

  • Looks like another reason to bring the troops home….. Then it would allow HDT to produce the civilian model. Would love one of these to commute on, but the price will need to somewhat reasonable…..

  • Until I have the opportunity to ride one I’ll take the chance of being a stick in the mud. I have such a hard time thinking that a diesel will provide the same thrill that a highly tuned sportbike can. They might be just dandy slogging around in the dirt or even cruising Main street. I just have a hard time thinking they can bring the same smile to my face compared to high performance road bike.

  • Ever read a ride report of the Hayes’ bike. Slow and shaky as she goes captain. Except for round the world types, it is doubtful that anyone would want this as a regular ride.

  • I have wanted to see this bike on the road since I read about it 5 or 6 years ago. A DP diesel bike sounds like a great ride.

  • The OEM’s can do a great deal in improving engines, if it will be profitable for them, otherwise it is up to the small companies. It will be interesting to see if Hayes Diversified Technologies is able to put together a street legal version of the bike they sell to the military or if it becomes too cost-prohibitive to manufacture for the general public. Also, will this technology be relegated to the Kawasaki KLR650 type of motorcycles? Gee, maybe something positive will come out of this ridiculous rise in fuel prices.

  • Not interested in a diesel motorcycle….. & the MPG doesn’t matter to me. I have a ’04 FLHT that probably gets ~ 40mpg…. That’s fine. I wish it didn’t cost me $15+ to fill the tank, but the pain is not great enough to go diesel. A diesel motorcycle just seems like sacrilege. Gas powered motorcycles are sacred to me.

    I remember back in ~ 1976-77…I was 19 or so & had a 250 Kawasaki F-11 Enduro w/Hooker Expansion Chamber…. Sounded like a full bore Motocrosser comin at ya…

    I was out crossin the moto’s at a place we called “The Jump’s” when I had to switch the gas to reserve…. I rode a bit longer & then headed for the gas station close by. I dug deep into my pocket & pulled out…… a quarter.. as in 25 cents! That’s all I had so in went the 25 cents worth of gas. Between the mpg & the cheap gas, I could ride the rest of the day & then home with gas to spare!

    Riding a motorcycle is part of me…it’s not to be messed with. It is my escape, release, hobby, lifestyle, tradition, etc… it’s me! I refuse to let the cost of gas take that away or in any way demean my riding experience. Other areas may be cut but not the bike! That’s staying!

  • I think that the idea is very interesting, the good news is that diesel engines these days produce good horsepower when mated to a small turbo and even without the turbo they make decent power but need to be bigger. They are very clean and if made right quiet. The downside is that they have very, very expensive parts and requiere expensive maintenance.

    I would like to see alternatives like diesel giving me 100mpg, since my everyday ride zx7r (naked) only gives me 31mpg and the gas price is at 6 USD (Dominican Republic) I could see myself everyday in one of those.

  • Not an automotive or motorcycle engineer, just a rider. I think that the big four will do what they have to do to satisfy a lucrative market. I’d love a 100 mpg bike, but that’s just me. Most riders are riding for pleasure, not to save gas money, and a lot of the pleasure comes from performance. Its not realistic to expect a 100 mpg diesel to satisfy those performance needs.

    If a big market develops somewhere else in the world then maybe we can get the 100 mpg bikes developed for that market – that’s if the manufacturers think they can sell more than a few hundred in the States.

    In countries where a large portion of the population is too poor to own cars, a more fuel efficient bike is not their dream come true, an affordable car is. The Nano is a good example.

    To be anything other than a novelty, the bike would have to be relatively cheap, say 5 to 7k, to justify the fuel savings. I think Hayes is looking at about 18k for their diesel KLR, if they ever bring it to market. At that price it’s pure novelty. Anyone who can afford to pay that price for a mediocre performing bike can afford expensive gas. According to their website their bike gets 105 mpg at 45 mph. What does it get at 75 mph? Maybe a lot less, maybe even in Ninja 250 territory.

  • Heh.. I think the first 100 mpg mass produced car “should” actually be a motorcycle. If they put a tenth of the engineering effort that they do into “performance” into “efficiency” instead I’m sure they could arrive at some outstanding numbers. Will they? Who knows. But I will say this. The first major manufacturer that builds a “real” motorcycle (as opposed to a scooter or some dorky buell blast) that gets 100+ will have a distinct advantage in today’s $4 to $5 a gallon country.

  • I like the idea of a diesel KLR650, but only one problem. I’m 5’6” with a 29” inseam, how would I ever ride it? How about a version with a little less off road capability, but that I could ride.

  • Since the cruiser boys are most concerned with torque, and those twins only rev to 7000 rpm anyway, Diesel and its 5000rpm max is a perfect fit.

  • I think the diesel KLR will be a dog. A one-lung diesel with no
    turbocharger would be like paying top-dollar for a brand-new 1990 PC
    with a 386 processor. Yes, it is fuel efficient, but the product is
    unusable in real life.

    Also, one reason diesel is more expensive now is that much of it is
    imported, and not refined domestically.

  • I’m not sure why this hasn’t been brought up before, but diesel vehicles are much more efficient at burning fuel than gasoline engines. I cant imagine how man MPG a diesel motorcycle would get, but here is some food for thought, the typical Chevrolet, Ford and Dodge 1-Ton trucks can get around 18-21MPG. People scoff at me when I tell them this but it is true. A diesel motorcycle would be awesome, I am a huge diesel advocate, I even subscribe to the Diesel Power Magazine, which keeps up with the “diesel world” if you want. I am very excited about the proposed ½ tons that GM is supposed to be introducing with 6 cylinder diesel engines, they’ll probably get around 28-30 MPG.

    I say build it, I’d buy it!

  • It is sad that my 2002 New Beetle TDI gets the same MPG as my
    motorcycles. I’ve thought about the KLR / Diesel conversion bike, but
    they priced to at $16K! While it is cool that the bike has a 600 mile
    range, not sure it is worth $10K over a regular KLR. I believe to make
    it competitive — it will need a small turbo to make it have reasonable
    performance. I’d seriously consider it – the ultimate adventure bike.
    Big tank – big range!!

  • As I pointed many times to many people and it could be used as product brief for any seriuos motorcycle producer:


    10000 – 11000Euro

    600 – 800cc twin
    60 – 80hp
    500 – 600km range
    max 175kg without fuel

    comfortable for 2
    good weather protection

    easy of loggage carrying

    good suspension with easy of adjustability for 2up, loaded/unloaded

    good on and off road abilities
    hardwearing durability
    easy of swap to supermoto
    long servicing distances – min 10000km
    ease of maintanance
    minimum is the maximum philosophy as for the body parts
    diesel is a plus
    This is all that will make a perfect bike, could just someone do it PLEASE

  • I can see diesel engines for “utility” motorcycles like dual sports and for
    touring motorcycles like a goldwing but I don’t see them working well for
    sport or general purpose motorcycles due to the increased weight.

    I would like to see an OEM prove me wrong by building a Ninja 250 type bike
    in diesel form to see what it would be like weight and performance wise but
    I don’t expect to see that happen very soon.

    I would think it more likely the small displacement high mileage diesel
    engines would find there way into scooters first.

  • There is a company in the Netherlands that has been producing a diesel sportbike for a while now called Star Twin Motorcyles (see attached PDF spec sheet)
    It is called the Thunder Star and uses a 1200cc triple turbo-diesel from a VW Lupo.
    Horsepower – 70 hp
    Torque – 118 ft/lbs
    Weight – 450 lbs
    Fuel economy – 93 mpg!

  • I worked on a project mapping NOx levels for diesel applications. When it
    comes to meeting low emissions the technology is definitely there.
    However, companies are extremely tentative about sharing any information
    on their progress, even to university research projects.

    The catalytic converters could be made small enough to fit appropriately
    on a bike. The problem is that diesels have a compression ratio twice as
    large as a gasoline engine. This will mean heavier engines to cope with
    the added stress to the cylinder walls. Diesels also have a harder time
    starting in cold weather, so those riders that like to get out when the
    temps top the freezing point may have a few problems getting their bikes
    to turn over.

  • I was sold on the ideal of a diesel motorcycle when I first read about the Twin-Star Thunderstar at

    That thing has enough torque to pull out a tree stump, and enough fuel efficiency to get you from hither to yawn.

    So, why haven’t we seen these bikes on our showroom floors? ummm…Emissions? Cost? Yes, that’s the reason.

  • I think engineering wise there’s not a great step up to be found,
    since the people doing the military conversion are using a top of the
    line motor. But the major advantage of seeing a major name-brand
    building the bike of the future, is price. They’ll be able to tool up
    and build the massive quantities the masses need.

  • HDT has offered the Civilian model but is currently not making them and at $19,000.00 is really not obtainable to a large group in the Dual Sport arena; but I do believe the diesel motorcycle market is ready if the admission price is not too high. When the coal to diesel or other bio-diesel(clean burning)is more readily available I think the potential customers will embarrass the idea. I’m ready now. Can you imagine a VN2000 diesel?

  • I’d buy one, but not for the price Hayes was going to charge. I don’t think they will be as successful in the private sector unless they can come down a bit from Pentagon price levels.

  • The idea of a diesel motorcycle seems like a good idea but the reality of sitting atop a super high-compression engine has the down side of extraordinary combustion noise. Years ago I had the opportunity to sell Polaris ATV’s at a store selling Japanese products and the Polaris Sportsman Diesel came out. If you rode these diesel ATV’s for about 5 minutes in the parking lot your ears would begin to ring. We all tried to avoid riding it after a while.

    If a diesel is to be made practical, and I doubt that the quality of power will attract more than a few, it will have to be sound insulated with a shroud of some kind.

  • I think it about time light, responsive, fuel efficient and clean diesels made it to the motorcycle world. We’re not talking big truck engines, but small 500-1000cc turbo’d torque monsters that will take bikes to the next level of clean/green performance machine!

    Look at and tell me bikes have had the same fuel economy improvement in 30years that small cars have had. I don’t see it – an 1980’s XT500 used to get 60mpg (imperial). Throw in how qucikly we burn tyres (lots of petro chemicals there) and I doubt there’s currently a strong green argument for bikes vs the new generation of cars. We need to make a paradigm shift in the industry to put bikes back at the forefront of technological innovation, and in particular environmental – without losing performance. Modern diesels could be the (or at least one of the) answer/s.

  • As I understand it – the reason behind the U.S. Military buying diesel
    motorcycles is not for MPG concerns, but logistical ones. One fuel to
    run many vehicles cuts down on the nightmare of getting the right fuel
    in the right spot for the right vehicle and prevents operations from
    grinding to a halt when something screws up and the ‘right’ fuel isn’t
    there. Its ALL the ‘right’ fuel.

    If motorcycles were purely about cost savings – then I’d see a real
    future with diesel power. However, motorcycling isn’t just about
    transportation and cost savings. Europe has embraced diesel FAR more
    than America. Are any of the majors fielding diesel-run models? I
    don’t believe so. Even the Europeans want a little bang with their
    buck. Diesel’s performance leaves a lot to be desired. Particularly
    when placed next to commuter bikes like the Ninja 650r that aren’t
    even performance oriented. If they were to develop an engine that
    would perform on par with gas – similar to Audi’s LeMans race cars –
    then perhaps.

    Then lets consider the cost. There’s little chance of a diesel
    motorcycle being at a price point to make it sensible as a penny-
    pinching choice. Is it reasonable to think that a diesel-powered
    bike, likely built in small quantities due to lower demand, will cost
    anything close to the $6,599 Ninja 650r and bikes of that ilk? Highly
    doubtful. So – beyond the early-adopters and people that just want
    something ‘different’ – the gas-powered bike still makes more sense.

    Neat idea, but still just a novelty.

  • I’ve been saying for some time now that when I retire in 2028 I should be able to buy a Gold Wing that’s turbo- diesel powered and gets about 80 MPG (75 MPG, or so, when pulling a trailer….Ha!)

    Let’s band together and tell Honda to get crackin’ on this.

    Seems to me that the cruiser market would also be a natural place for diesels, with the sounds and smells adding a dose of character to an increasingly, and perhaps overly refined sector of the motorcycling spectrum.

  • I’ve had diesel cars since ’79 and the advances have been
    wonderful….the new 320CDI ‘Benz is indistinguishable from it’s gas
    powered sister…the problem when trying to translate to motorcycle
    use would be, IMHO, the need to make the diesel’s engine at least a
    four cylinder……and it would be a wonder in an ST1300
    format….but it would also cost 20% more than the gas model and no
    faster… might go 500 miles on a tank of bunker oil but I’m
    thinking the American pain threashold is $7.50/gallon.

  • I just got a new 250 Ninja and you have to thrash it constantly, speedo
    is about 10 % optimistic and tach shows 8200 rpm at 65 mph with the
    Dunlop tires. I am going to gear it up as soon as sprocket is off back
    order. Only 750 miles so far and not really broken in, but 44 mpg.
    About the same as my Yamaha SRX. Great fun though, can rev it up and not
    worry about the license. Saving gas is a really poor excuse for riding a
    bike, better off finding an old Geo Metro. Diesels? Tractors and trucks,
    not motorcycles.

  • Now that gas has exceeded $4/gallon, Americans who have never owned motorcycles are now seriously considering them as a way to reduce the costs of everything from errands to the daily commute. That’s where a diesel motorcycle comes in. Many automobile drivers would be thrilled with a motorcycle that had a high-efficiency diesel engine, automatic transmission, got 150mpg, had ABS brakes, and got to 60mph in under 8 seconds. That’s really easy to accomplish in a lightweight, manageable bike using today’s technology.

    The motorcycle manufacturers just need to ignore the guys whose manhood is insulted at the thought of a bike that’s quiet, has an automatic transmission, doesn’t win races, isn’t slathered with chrome, and does not have a name that sounds like a sex toy (e.g., Intruder, V-Max, Night Rod, Rocket III, Softtail). They aren’t the target market.

  • I’ve often wondered why certain segments of the motorcycle market haven’t embraced diesel motors. I’m sure it’s partly down to the availability of low-sulfur diesel that is only now arriving in the US market. The relatively huge amount of torque that can be produced compared to gasoline engines would seem to mate perfectly with the scooter, daily driver and cruiser markets. The only drawback I can see is the inherent noise and weight of the diesel motor. The noise issue has vastly improved in the past several years (some of the European automotive diesels available from Ford, Audi, etc. are reportedly nothing short of astounding) and the added weight is only a marginal drawback when considering the non-sport market if one were purchasing for mileage/drivability/torque considerations alone.

  • Diesel Motorbikes probably have great potential. But there isn’t really incentive for research to develop them.

    Considering the innovations from racing that have flowed through over the last few years to real world bikes from racing…It would be great to see something like one of the major racing competitions eg one of the support for the Moto GP such as the 250cc class were made to be diesel only. I am sure that a heap of research would be done and in no time we would have practical diesel bikes. They would be also seen to be promoting a more ‘green’ side of the sport.

  • My hopes for anything related to higher mpg for motorcycles and or even cars for that matter do not lie on the shoulders of big manufacturers. I think the small companies are the ones to make things happen, look at things in the past. I spoke to a customer of mine just this past week involving HHO (Hydrogen split from ordinary water) to fuel a internal combustion engine. Now granted, this setup he has running right now is on a 1928 Ford Model A truck, which is a very low HP engine and an old design, it will however idle on pure HHO, if you hit the gas pedal it dies, simply not enough supply to meet the engines demands. The manufacturers however don’t even have something like this, the market infrastructure can’t make money selling “fuel” at Water Stations. The trend I see is that the businesses are so inter-twined with each other that they also are patting each others backs. The little guy wants to stick it to the man, so they will go in further with their own ideas, but the reason most do not succeed is big investors at times won’t fund these. Big investors have money in other big corporations which could take a big hit if some of these new technologies made it to market, just like the famed 100mpg car back in the 60’s or 70’s we all have heard about.

  • I wandered across the Hayes Diversified diesel motorcycle site a few days before your recent article, and of course, I am interested a new MD 670 F. However, considering the proposed price near $20,000.00, the fact that Hayes Diversified has devoted all of its production to the military bike for years, and the probability that the oil war in Iraq will be over soon, I wonder if there will be a supply of surplus military versions of the diesel motorcycle available in a year or so. This may be my wishful thinking on several fronts, but do you have any sources to address a future supply of military surplus versions of the diesel motorcycle?

  • Check out this link:

    It should appear on Dutch roads sometime this fall.
    With far better looks than what’s on the website at this moment.

  • You asked for us to “send you our thoughts” about diesel motorcycles. Well I have been doing that for years. Each time you ask about a better way to do something (better mileage, more dependable bikes, etc.) I try to point out what HDT has been doing with their 650 dirt bike or point at what Star Twin has accomplished by adapting a VW Lupo motor to a sport bike. This is a very viable option for the motorcycling industry. The biggest draw back that I see is the buying public equates diesel with Cummins, Freightliner, or something that outweighs a house. As the afore mentioned examples show that doesn’t have to be the case. Even in the automobile market the best mileage cars are very light little diesels.

    Then there is the renewable energy side of the equation. Why is gas and diesel becoming so expensive? BECAUSE IT IS A FINITE RECORSE! The oil companies have sucked all the easy stuff out of the ground and their production costs can do nothing but go up, so we pay a lot more at the pump. Arctic Cat has seen the light and offers a 700cc diesel quad. They are promoting the fact that it runs on Bio-diesel. They have even been spouting the words of a great inventor of more than 100 years ago. That is to provide the farmer with a work vehicle that can run on a fuel that he can grow and process on his own farm. Yes, Dr. Rudolph Diesel, we hear you.

    And maybe after the farm work is done we can put some of the same renewable fuel in our two wheeled toys and go play.

  • They may make them for the US Military, but they’ve been promising a
    civilian version “next year” for probably 5 years now. Seems like a good
    thing to bring out, but we’ll see when, if ever.

  • This is BS. HDT has been promising the civilian deisel KLR for about 5 years now and it’s always one reason or another that they can’t deliver. At one time they even had a price listed of about $19,000, which as far as I know, people are still laughing about. I’m sure you will get the same story from everyone on, so don’t take my word for it.

  • I’ve been a reader of your site for quite some time now. As a diesel engine development engineer and a student of motorcycle design, I feel I can give some intelligent feedback on this topic.

    I think a diesel motorcycle is an interesting and exciting design challenge for both the diesel engine and motorcycle engineer. 70 kW out of a 1.5L diesel engine on a larger touring bike (think BMW K1200 or a GoldWing) would be a very good fit – lots of low end torque, ample power for the highway, and easily 60-80 mpg cruising. However, diesel motorcycles face a contradiction in terms of design. Motorcycles prefer smaller, lightweight, power dense engines to keep the weight, cost, and complexity down. Diesel engines have started to approach the performance capabilities of a spark ignition engine, but only in a very highly tuned and developed state – compound turbo charging, extreme cylinder pressures, and complex fuel systems. The adaption of a diesel to a motorcycle will require compromises and sacrifices of many technologies such as turbochargers, aftercoolers, and expensive fuel systems and controllers in order to meet other functional requirements such as weight, cost, transmission limitations, and packaging.

    I think for specific applications where outright power is less useful than torque and usable power, a diesel engine may very well be a viable option. Dual Sport/Off road bikes (such as the KLR650 mentioned) are an easy leap, touring bikes with less packaging constraints also may be an option, and the fuel economy would be a huge advantage in that market. The potential is there, however the high costs of developing a diesel engine to fit this application reserve the task to a major OEM with a significant development budget and production volumes. Any sort of boutique or low volume manufacturer will have a more difficult task of justifying development costs with low volumes, or they would have to price themselves at a point where most buyers would not even consider it a real option. Due to much higher torque output, conversion of a gasoline engine is a very difficult task, and nearly every component of the engine from the output shaft to the valve cover will need to be reworked or replaced.

    The real question is how emissions will be controlled, as this has the largest potential impact on cost. I do not have the technical background on the specific motorcycle test cycle and emissions regulations (I work in the heavy duty diesel industry), but I can comment that small displacement diesel engines (less than 2.0 L) have a very difficult task in controlling emissions. If any sort of aftertreatment is needed, the design envelope becomes even smaller and more difficult as items such as particulate filters and catalysts have specific packaging restraints and are not cost efficient on smaller engines.

    Unless BMW (who has significant small diesel engine experience with their European car models) or one of the Japanese manufacturers make a push for a diesel motorcycle, you are unlikely to see a real production model. These makers’ volumes are to the point where they would no longer be exempt from the Tier 2 standards, making the task even more difficult. Boutique or retrofitting may be a possibility, but not in an economic manner, which is the whole point of a diesel. Unless one of the big OEMs gets in the game, diesel motos are just not going to happen.

    Thanks for the opportunity for the feedback, and keep up the good work.