Air-Cooled vs. Water-Cooled

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Most of us have  a preference for one – or the other.KZengine1

I own – and have owned – numerous examples of both types. There are pros – and cons – either way.

My ’76 Kawasaki Kz900 is, of course, air-cooled. To be precise, it is air and oil-cooled – as all such bikes are. The engine castings are finned for a very functional reason: to help transfer – to radiate – heat away from the engine to the cooler surrounding air and so that airflow over the fins (and so on) can do the same thing. But oil is also used to keep the engine cool (as it does in water and oil-cooled bikes).

Because there is no other fluid to help keep things cool, the oil has to work harder in an engine sans water jackets, radiator and so on. It gets hotter – and thinner – faster. This is why many air/oil-cooled bikes have external oil coolers (mini-radiators, except for oil rather than anti-freeze) and – in some case – deep sump or additional capacity oiling systems.'76Kz900

If the engine is well-designed – and factory stock – and in good running order – usually, it will not overheat. However, if the engine was not well-designed, or if it’s been modified to produce additional power – or it is not in good tune (running lean, for instance) it is more vulnerable to overheating and to heat-related damage.

I have modified my Kz900’s engine to make more power. It has received a set of high-compression pistons and its displacement has been increased to 1015 CCs.

It makes more power now – but it also runs hotter. Quid pro quo, Clarice.

Here we come to one of the downsides of an air-oil cooled engine: Power production is limited (at least, as a practical matter) by the engine’s ability to shed heat.  Kz engine kit pics

The Kz’s plant is a DOHC four – the same basic layout used in many modern superbikes that have 180-plus hp and 180-plus MPH top speeds. But almost all of these engines are water-cooled. Because making that kind of power makes all kinds of heat – too much for air and oil alone to deal with. My bike’s factory hp rating was 82. I’ve pushed that to around 120 or so. This approaches the limit of reasonableness for an air-cooled street motorcycle engine  . . . if, that is, you’d like it to last. Drag bikes powered by the much-hopped-up versions of the old Zed big four make a lot more than 120 hp – but they only have to live for a few passes down the quarter-mile.

No idling in traffic when it’s 95 degrees outside.

For power – and reliability – you will find that the air-oil cooled layout’s limits are much lower than they are if the engine is soothed by water.ZRX12002

On the other hand… .

Air-oil cooling has a number of plusses to argue for it, too: The layout is inherently simpler. There are fewer parts – you eliminate an entire system from the bike. No radiator, no hoses, no water pump. That means less in the way of regular maintenance chores, as well as  fewer things to potentially break down the road and cost you money. It also means – usually – that the engine will be much more accessible and easier to work on. As well as prettier – because the engine will be cleaner – less obstructed from view by all the aforesaid stuff.

That’s worth something, surely.

A few years ago, I was out riding my ’03 Kaw ZRX1200 – a modern sport bike with a water-cooled engine. The temp gauge began to edge up to the unhappy zone and as I rolled up to a red light and stopped, I caught the can’t-mistake-it-for-anything-else aroma of anti-freeze burning into steam. My bike’s radiator had a pinhole leak – probably caused by a piece of road debris chucked into it at high speed as I was blasting down the highway a few minutes prior – and a jet of coolant was spritzing the headers. Luckily, I was not far from my usual bike store, so I gimped the Rex there – just barely making it before the needle went all the way red as the last of the coolant bled out.Rex radiator

The new radiator cost me $400 – not including labor to install (I was sans tools and at their mercy).

Even if that never happened, it would still be necessary to periodically drain/refill the system with fresh coolant. Check – and, eventually – replace the hoses, thermostat and water pump. It’s part of the deal. And water-cooled machines are prone to scale build-up and rotting of threads exposed to the coolant. A 40-year-old air-oil cooled bike has no such issues – but you have to be really careful about buying older water-cooled bikes. If the radiator of a 40-year-old bike is crusted up with scale, bet your bippie the inside of the engine is, too.

You’ll never have that problem with an air-oil cooled bike like my ’76 Kz900 (or my single cylinder dual-sport). leak 1

In fact, if you leave the thing alone – no high CR pistons, overbores and other such – and simply change the oil and filter every now and then – you’ll probably never have any problems, period.

A water-cooled sport bike might get you there quicker – but an air-oil cooled one will always get you there.

And that’s all I have to say about that.

Throw it in the Woods?


  1. Yeah Bevin,

    When Dean Norris said he played “a really good guy” in Breaking Bad he laughed a long time afterward. Not in an ironic way, but in a subconscious way, indicating he really didn’t believe it, I think.

    There is a science of morality, and against our will, we give off tells and confessional cues that what we are saying or doing are not in harmony with our morality.

    If one is astute and observant, one will pick up on tells of people that confess quite scientifically just how confident they are that their actions are right and proper.

    If one looks at human conduct purely scientifically, like Thomas Aquinas or Confucius, one can glean much useful data out of mainstream morality and prole control.

    For this work to have true scientific merit, one must take moral theory down from its altar and make it fend for itself in a laboratory setting. Both Aquinas and Confucius taught that religion or morality, are just sciences, not things to be imposed by the force of the state.

    In terms of Western morality, the Hank Schraders of the world are guilty of wrath, pride, envy, greed, vainglory, and acedia. I’ll leave it for a later time to discuss where Hank fits under Confucius’ Jen, Li, Yi, Hsiao, Chih, Chun-tzu, and Te, categorizations.

    In contrast to Hank, Walter White could only be said to be violating the artificial statutes of Earthly Kings. He had a moral reason for his actions, and acted only in legitimate self-defense. The force of arms or law does not imply morality.

    What has been sold to modern man as 7 deadly sins aka as the 7 capital sins; and the 7 virtues, are aspects I would recast as being 7 aspects of wealth, and 7 aspects of wealth accumulating behavior.

    The ancient sense of the word demon, is merely one of being an abstract force. The virtues are ways to achieve wealth, and to possess great force. The virtues being chastity, temperance, charity, diligence, patience, kindness, and humility. Without state interventions, their would be six additional coins of wealth, besides the one we’re all used to: Mammon and greed.

    Once you abandon the superstitious undertones, you’ll find the 7 types of wealth, and the 7 virtuous forces(demons) of capitalism, have great explanatory impact:

    Lucifer – pride. A person basks in their pride, and experiences it as a kind of wealth. They can bank on their reputation.

    Mammon – greed. A person feels safest when they control a large pool of resources. Greed leads one to conserve their capital, and to be able to weather the cycles of boom and bust.

    Asmodeus – lust. Lusting after something is motivational. You may make extraordinary efforts. If you possess great lust, you may likewise be highly productive. If you are an object of lust, that is a natural form of wealth. You can trade for all manner of other capital, based solely on the lust of others wanting to make an exchange.

    Leviathan – envy. This simply means you want to be the best. One is willing to go to great lengths because of envy. This leads one to attain a great many skills, to work hard to achieve excellence. If you are seen as one to envy, it is a source of great wealth. You can trade with others, who will bribe you or give you other things, so as not be someone they need to envy.

    Beelzebub – gluttony. Gluttony means only a heightened ability to enjoy one’s wealth. What is the purpose of having if you don’t enjoy. Use it or lose it. Having a great appetite can cause one to be greatly prolific, and to attain great knowledge and expertise about such things as one has an appetite for.

    Amon/Satan – wrath. This is tied into our animal natures. If you lack wrath, you lack self-preservation. You lack the will to protect yourself and your wealth, you fail at self-defense. One must attain wealth, and one must also protect said wealth. Those who possess great wrath, can trade their spiritedness for other forms of wealth.

    Belphegor – sloth/acedia. Everyone needs a day of rest, a sabbath. All work and no play makes you a dull boy. Taking it easy, getting enough rest, these are all important for sanity. Acedia, neglect of duty, can often be a good thing. Not all imposed duties are beneficial. Sometimes the best course is to let things slide. This to shall pass. Being slothful, can lead you to have a lower threshold for what you consider being wealthy to mean. If you’re truly happy, with only a crust of bread, that puts you outside of the rat race, and all those hierarchies that you might best avoid in the first place.

    – Mystical and non-scientific minds will try to drag all manner of irrational and unsupported things into this discussion. Let them say their piece. But then ask them what is their proof. What is their basis for their claims.

    Make it clear, that asserting “greed is bad, because my English mis-translation of ancient texts says so”, is not a valid nor scientific claim worthy of discussion nor response. Especially because the texts were cherry picked, and used out of context by the English Kings and others to hold onto power.

    Ancient morality was once as rigorous a science as any other. It can be made so once again with a little diligence. In the days before surplus wealth was common, it was a science to be practiced or else, a science that meant one either survived or one perished.

    • Dear Tor,

      “When Dean Norris said he played “a really good guy” in Breaking Bad he laughed a long time afterward. Not in an ironic way, but in a subconscious way, indicating he really didn’t believe it, I think. ”

      I hope you’re right and I’m wrong.

      I’m going to watch the clip again. I only watched it once. Might have missed the subtext.

      By the way, have you seen “Dallas Buyer’s Club?” Surprisingly good!

      Not the Hollywood LGBT PC aspect. That was an irrelevance in my book. The part that had me cheering was the hero’s defiance of Big Pharma and the FDA, a racket disguised as the “public interest.”

      • Yeah,
        I think you were right about Dean. He accepts Hank as a hero unquestioningly.

        But much of what we do is largely involuntary. Laughter comes from fear. From the unknown. Love to get a 2nd opinion on what you think all the laughing “means.”

        I’ll check out DBC. This whole gay/trans thing is unavoidable. Especially when watching things from England and the UK.

        I want to watch whatever is the most advanced and intelligent. If I have to slog through all this top down agenda of the days of males waning and coming to an end. So be it.

        If LGBT can make a go of it on its merits, and decouple from its current place in the high court of militantly enslaving the masses of other modes of sexuality, then I’d have no issue with it.

        I just finished watching Snowpiercer. I thinks its indictment of humans controlling human destiny is spot on. Whatever it takes to derail this farcical train to nowhere, is probably worth it.

        Ideally, it can happen without loss of a single life. Each person represents infinite wealth, if only they can use their abilities against the chaos of nature, and not to construct hierarchies to enslave their fellow men.

        Possibly all human advancement and knowledge is linked to the train of psychopathy. If so, then mankind must start from scratch and find new peaceful and productive ways of harnessing the chaos of nature without violent hierarchies and human sacrifice.

    • Dear Tor,

      I agree with your take on the two characters.

      Hank Schrader was a clover. In fact, he was an uberclover.

      Walter White, on the other hand, was merely a supplier meeting a consumer demand. What he was supplying was of course a dangerous substance. But it was exactly what consumers wanted from him. It was quality merchandise that resulted in him “building his brand.” They were satisfied customers. Whether they should have been customers in the first place, is of course up to them.

      When Schrader’s wife blamed White for her husband’s death, and White agreed, I was pretty pissed. As I saw it, she had the morality exactly backwards. White’s guilt was “unearned guilt.”

      Schrader got himself killed by insisting on being an unregenerate uberclover and meddling in free trade.

  2. question regarding msrp of Yamaha SR400 vs msrp of Honda CB500F.

    The Honda is (470cc), water cooled and about $500 less than the Yamaha.

    What could be some reasons for the higher price of the Yamaha?

    Is the difference due to
    — quality?
    — quantity available/ being sold worldwide?
    — cost of materials used?

    If I was planning to keep the motorcycle for many years, then the cost difference wouldn’t deter me from getting the SR400. However, since the SR400 is simpler and I would think less costly to build than the Honda CB500F, I would expect the msrp to be closer to $5,000 than $6,000.

    Does anyone have possible explanations for the higher msrp of the SR400 compared with the CB500F?

    • Dear Mith,

      The Yamaha SR400 is such a nice bike I wouldn’t let a 500 dollar price difference influence me.

      If I were a motorcycle guy, I would get it. The concept is just so appealing. It’s so an intelligently optimized. About as large as a single cylinder bike ought to be. So basic and simple.

    • Hi Mith,

      I am looking into this; actually, I have an article in the works about these “return to a simpler time” bikes… stay tuned!

      • Dear Eric,

        Looking forward to that!

        The same principle ought to be applied to cars too.

        Use new tech when it constitutes a genuine advance over old tech, when it gives a new car far more longevity, fuel economy, horsepower over the old.

        But at the same time, “KISS.” Scrape away all the encrusted bells and whistles that don’t actually help you get from point A to point B, which after all is said and done, the raison d’etre of an automobile.

        Obviously it would be far easier to do without goonvermin crap such as air bags and five mile per hour bumpers. But as much as possible ought to be stripped away in order to arrive at the automotive counterpart of the Yamaha SR400.

    • @Mith – Do not make the decision on price or pure looks. You will have to ride each for an hour (if you can get it that long) before you know which fits your body and liking. You will definitely feel “a difference” after some time in the saddle. From experience I will never buy any bike without an extended test ride that tells me I can live with the ergonomics, seat and engine power band. A five or ten minute ride is worthless. That happened to me after I bought a Suzuki V-Strom. Great bike, but I could not make it “fit me” for any extended riding. I went and sat on a 500F and it felt “right” for “me” sitting on the showroom floor, but I was not there to buy a new bike.

      Another ting to look at is factory maintenance recommendations like valve adjustment, plugs, chains, oil change intervals, tire (size cost) and such. Some are long and some are short. If you are paying the shop for parts and labor it can add up fast.

      • Dear Gary, Mith,

        No argument with Gary.

        My remarks were predicated upon the assumption that neither choice was problematic in other respects.

        By all means, test drive both.

      • Garysco,

        Good point about being sure the MC fits you well.

        How can you get an extended test ride? I was under the impression that dealers did not give test rides of MCs

        I did not factor in the maintenance costs & repair schedule.


        I agree that $500 should not be a deciding factor.

        Still I am somewhat curious to know how the msrp is determined. In Europe, the cost of the same bike is often significantly more than in North America.

        • @Mith – I don’t know, other then convince them you have the money / credit and are going to buy something. But you want to take it out for X miles or time before deciding. If I am not mistaken BMW will still let you test ride overnight. Maybe pick a similar BMW model and threaten the Yamaha/ Honda sales guy and his boss. Eric may have some ideas.

          A couple of years ago I bought a 2008 Kawasaki KLR 650 dual sport. Lots of fun and much much cheaper then a BMW GS bike. I put crash bars/ highway pegs on it and also had the local motorcycle seat upholstery guy (awesome craftsman) widen the bench seat foam 4″ inches & make a nice custom cover. I could ride that bike 400 miles a day and net feel any pain at the end. A guy came by in a parking lot one day, saw the setup and offered me what I paid for it 3 years and almost 20,000 miles ago. He now has the keys. There are days I miss having it to play with.

  3. Eric,

    under UK specs:

    Maximum power 17.1 kW (23.2PS) @ 6,500 rpm
    Maximum Torque 27.4 Nm (2.8 kg-m) @ 3,000 rpm

    If North American mc same as UK then it should be able to get to 75mph w/out straining the engine. (guessing about 5500 rpm @ 75 MPH, but I will need to look into this further.)

    • I could never fathom kw and PS as ways to measure power!

      But, this bike should have output comparable to – if not better than – 450/500 CC bikes of the late ’70s and early ’80s. Which means, plenty of power.

      Some perspective:

      One of my bikes is an ’83 Honda GL650 Silverwing. The twin cylinder engine makes about 60 hp – and is sufficient to get this fully faired (front fairing and windshield) and saddle-bagged touring bike through the quarter mile in about 13.4 seconds (quicker than most ’60s-era muscle cars) and cruise all day at 80 on the highway (top speed is about 115 MPH – drag limited, due to the windshield and fairing).

      This 400 should just as quick – and at least as fast.

      • The Yamaha SR400 looks great. It is now high on my consider list. Another possibility is a new Royal Enfield, what do you guys think of that Indian-made bike?

        • I’m hoping to get some seat time on all these bikes; the problem is the bike MFGRs do not maintain big “press fleets” the way the car companies do.

          But, look for an article soon!

    • According to Convert units
      HP (0.746 kW = 1 hp)
      17.1 kW = 22.9 hp

      Torque (1 Nm = 1.35581794833 foot-pound force)
      27.4 Nm = 20.20 foot-lbs

      Comparing to a 2011 Honda CBR250R
      From Motorcyclenews
      Max power 26 bhp @ 8500rpm
      Max torque 17.6 ft-lb @ 7000rpm

      2015 Yamaha SR400
      Max power 22.9 bhp @ 6500rpm
      Max torque 20.2 ft-lb @ 3000rpm

      It seems the SR400 has slightly less hp but more torque than the CBR250R.

      I am estimating (more like guessing 😉 ) that the 0-60 time of the SR400 will be slower than the CBR250R (but not by much), but the SR400 will have more useable power at lower rpms

      From NZ
      2013 SR400
      Max Power 27 hp @ 7000 rpm
      Max Torque 6.3 kg-m @ 6500 rpm (about 45 lb-ft)

  4. Hey Bevin,

    Wonderin’ if you ever caught any of that Under the Dome series?

    Under the Dome – Season 2 Preview

    Under the Dome Season 2 – Starts June 2014

    Freud used the terms “occult,” “spook-complex” and “mysticism” in relation to Jung’s interests. In a letter to Jung from May 1911, Freud warns Jung:

    “I know that your deepest inclinations are impelling you toward a study of the occult, and do not doubt that you return home with a rich cargo.

    There is no stopping that, and it is always right for a person to follow the biddings of his own impulses. …

    Only don’t stay too long away from us in those lush tropical colonies; it is necessary to govern at home… .”

    Freud was attempting to put a fence around his newly formed school of psychology, psychoanalysis, a fence that would serve as a “dome,”
    – – –

    In these destructive “Under the Dome” ideologies, masses of people are often killed, tortured, and/or exiled. Think also of the beliefs and worldviews of ignorance that control the pathway of human endeavors.

    For example:
    1 The discovery of the Americas was impeded by the European intelligensia who believed the boundaries of civilization to be marked by the abyss of a dreaded domain of incomprehensible existence and possibly guarded by other-worldy creatures. (At the edge of their maps, they wrote “There Be Dragons”!);
    2 The nature of infectious diseases was attributed to many would-be origins until Louis Pasteur and others discovered the existence and nature of pathogens that spread disease, one of the most significant findings in medical research that did not occur until the middle of the nineteenth century;
    3 The political disharmony over the nature of alternate sexuality that presently hangs on conservative political and religious fallacies imposed by force.

    Fallacies that ignore emerging medical understandings of sexuality as having mainly a sociological and biological origin.

    Dean Norris – Big Jim from UTD and Hank from Breaking Bad. Portrait of the soldier/cop archetype – The View

    Escaping the Dome – the Collective Worldview

    Yes, at the very end and in Freud’s heart of hearts, he recognized the truth that each of us knows on the deepest level: there are indeed more things in this world than our philosophies allow for.

    Once we pass from beneath the stultifying dome of our lives, we catch glimpses of other worlds and beings and meanings.
    What is maybe most remarkable is the fact that this should not surprise us.

    It should not be such a strange experience at all because such adventures take place each night in our dreams.

    • Dear Tor,

      I watched all of Season 1.

      Waiting for Season 2.

      It’s worth watching, but it’s not a “must see” show on the level of “The Walking Dead” or “Game of Thrones.”

      Mostly I’m watching it to see what the message is, to keep a finger of the pulse of popular sentiment.

    • Dear Tor,

      The Dean Norris character in “Breaking Bad” was actually one of the worst villains.

      Not entirely sure whether the authors of the show fully realized that, or meant to express that. But I’m sure my fellow libertarians perceived him as such, and rightly so.

      The virtue of Breaking Bad for me was that intentionally or not, it cast a very bad light on the “War on Some Drugs.”

      • My hope is AMC network is one of the last few refuges of American TV, where everything doesn’t have to “cast a light” and take a position.

        I think Vince Gilligan was just trying to make a cool and real seeming adventure through most of the series.

        The ending of it, seemed contrived and in fulfilment of the formulaic agenda. But anything in America is expected and nearly commanded to show that in the end the bad guy doesn’t really get away with anything in the end.

        You have to watch precode movies before 1934. Or from 1965-1972 there was a brief window where the court struck down a censor law, and all kinds of things were shown in American theaters.

        The G PG R X NC17 system was devised in the early 70s and continues to be used to censor America with an iron fist quite effectively.

      • Right on Bevin,

        As Hilarius Clintonius Once Said: It’s takes a Villianage.

        Town councilman James “Big Jim” Rennie is a spot-on convincing archetype of the modern American Authority Figure.

        Holy Warrior against Drugs and Punisher of any who attempt to live outside his little slice of the State.

        Keeper of secrets and Murderer of Whistleblowers and Traitors.

        Savior Strongmen of the Town. Hayekian Honcho of the Serfdom System. Everyman Keeper of the Civilian Order.

        Tribute Collector. Power Wielder. Alliance Forger. Master of the Watch. Stoker and Tender of the Flame of modern Mount Olympus PTB Gods.

        – If the SHTF and I end up trapped UTD, at least I now have an idea of what it’s gonna be like, and what I might try to make it bearable until I resume being free to come and go as I please.

        UTD – Big Jim Kills the Reverend

  5. You guys…. and your kick ass posts about bikes. I better get a bike this year! Or it’s Uber-fail time on my part.

    Reading your posts is making it very hard not to have one. …And I soo miss my old motor scooter.
    Thank goodness I’ve stopped having dreams about it, and waking up wanting to check the garage and see if it’s still there.

    “Air-cooled, no battery, single-cyclinder w/kickstart.”

    Mang that sounds nice.

    • Do it, Helot – and do it now. Before the weather warms. You stand a much better chance of getting a great deal on a Craig List/classified ad bike when it’s miserable outside (and the guy’ wife is complaining about how they need some money).

      Guy I know down the road recently bought a beautiful and pristine extremely low mileage full-dress touring bike that I swear-on-a-stack of Cycle Worlds looked showroom new for $2,100.

  6. Eric,

    Here is an updated classic MC:

    2015 Yamaha SR400

    Unlike some retro bikes that are modern interpretations of older designs, the SR400 is an authentic living classic which has been constructed to virtually the same specification as the original model. With its air-cooled engine and twin-shock chassis, this timeless big single represents a return to motorcycling’s core values.

    Air-cooled, no battery, single-cyclinder w/kickstart.

    It seems to be a reliable robust design that it simple to maintain and operate.

    • Yes!

      Kick start (and fork gaiters, too)!

      Also, stickers just under $6k.

      I predict this bike will sell big numbers – and if not, Americans really have lost their minds.

      • Eric,

        I hope it will sell well.

        I am not able to get one this year, but I do want to get one either new or mildly used.

        Do you know if this MC can easily cruise @ 70-75mph all day?

        • Hi Mith,

          It ought to be able to.

          A 250 CC bike can maintain 70-75; it’ll be straining a bit, but it can do it.

          A 400 should be able to do it without straining.

    • Dear Mith,

      Damn, that’s what I call a bike!

      The Yamaha SR-400 reminds me of the old British bikes. I always liked the old British bikes. Especially Triumph and BSA. Lean and mean.

      Apparently somebody at Yamaha decided to “KISS.” Thank god they did. Now if somebody will do the same at one of the major auto makers.

      Never was big on Harleys. Something about them just rubbed me the wrong way. They were just too bloated.

      • Bevin,

        The SR400 was inspired by the older British and Japanese designs of the 60s and 70s.

        You will recognize in the design style the purpose, simplicity and directness of a design that pays homage to the classic beauty of the best British and Japanese designs of the 60s and 70s.

        I like the totalmotorcycle website for information about MCs. It was one of the sites I went to when I became interested in getting my MC license endorsement.

        I thought I really liked the CBR250R, but the SR400 looks real cool.

        • Hi Mith,

          I could not find the horsepower number for this bike, but I’m guesstimating it’s around 45, which should be plenty to move a bike that weighs less than 400 pounds.

          My friend owns a 450 Nighthawk I’ve ridden many times and it has plenty of power. No problems at all keeping up with traffic on the highway. It only begins to show signs of working hard at around 85-90 MPH – which is comfortable envelope given today’s speed limits/pace of traffic.

          This bike should also be capable of at least 60 MPG – and maybe more.

        • It seems that all the manufacturers are jumping on the retro bandwagon. Triumph has the Bonneville retro with fuel injection that looks like carburetors & the old bench seat. Honda has the CB1100 throwback. While not retro there is a lot to like about the new Honda CB500X with mid to upper 60’sMPG and accessories. The NC700X is another sporty urban crawler with mid 60’s MPH, but kind of boring to ride.

          On the retro idea, I am seeing plenty of nice, well cared for older Honda Nighthawks, Kaws and Yamaha’s for sale under $2,000 on Craigs List.

        • Dear Mith,

          Yes. Noticed that passage later.

          Really love the design philosophy behind it. This is exactly what I was talking about for cars, applied to the realm of motorcycles.

          Cool minimalism
          The archetypical motorcycle. One cylinder. One intake valve. One exhaust valve. One exhaust pipe. No balancer in the engine. Not even rubber mounts between engine and frame. A pure and simple-cradle frame design. Nothing fake. Steel fenders. Steel fuel tank. Everything authentic. And, talking about minimalism: No electric start!

          This all adds up to the “less is more” philosophy we were talking about earlier. Fewer parts, fewer things to go wrong, greater chance that it will remain durable and reliable.

    • Mithrandir – did you mean “no battery”? Or did you actually mean no electric start? I’m having a hard time getting my head wrapped around a fuel injected bike with no battery.

        • Yeah Eric – I already knew that, just being a smart-ass. I started to post something along the lines of “must have one huge capacitor under the seat” or “it would take some awesome check valves in the system to hold fuel pressure all winter.” Anyway, it is a really appealing machine. I saw the classic British styling influence first glance. I can’t imagine that it won’t be a hot seller on “this side of the pond” especially with gas prices such as they are.

  7. My 1981 Honda CM400 (one owner- me) will be an antique in two years. Air-cooled – at 32K miles, it’s even on the original chain and sprockets. Nothing I’ve ever owned has been nearly this reliable.

  8. When I raced air cooled two strokes (RD-350/375) back in the 80’s with the AFM, I would tighten up the squish clearance, bump the compression and ceramic coat the crowns of the pistons. Two strokes even more so than four strokes rely on keeping the crown cool to prevent overheating the next charge as it comes up from the case. Same issue as the four stroke, different over-all effect.

    Two strokes are famous for dropping power when hot, but I got a clue watching Tony Nicosia going over the Kaw 500/750 drag bikes at the Fremont drags with a insecticide can filled with water. He was cooling the crankcases to keep power up. When all was said and done, the bike would carry 6th gear into old turn 11 at Sears Point from the first lap to the last, unlike that rest of the bikes that would have to gear back to 4th in an effort to get to the corner!

    Many years ago, I posted a lot of articles about building two stroke engines. Just search on “Squishing Things Until They Give Power”. I have no dog in the hunt anymore, I don’t build engines now and the articles are free. Your mileage may vary…

    • Dale – I’ve read your stuff and I’m pleased to see you posting here. Thanks for the wealth of info on 2 stroke performance. I was the happy owner of a 1975 RD-350 ‘back in the day’ and I miss that little crotch rocket. Never raced it…well…not on the track anyway, but I did notice performance issues in the summer (Ft. Walton Bch., Florida). This was especially a problem when we’d have to sit idling in traffic for long periods of time. That little engine would literally cook you sitting over it at idle. If conditions permitted, we’d break ranks and lane split just to get air moving over the moter (and our bodies)! I also noticed that the bike ran a lot better during cool weather, but at the time I just wrote if off to the denser charge from the colder intake air. I’d never heard of the squish band until I read your stuff. For those of you that may be interested in the finer technical points of making the ol’ two-smoker scream like a banshee and keep screaming lap after lap, here are Dale’s most excellent articles:

      • Boothe, I remember people having a nitrous injector on the head(s)during WOT that helped a lot. Don’t recall it being legal in every category. Seems like I recall also that being outlawed in any form but there was always nitrogen….until they outlawed that. I didn’t understand their thinking on that.

        i also remember somebody(Smoky?)having a car with a closed frame, a hollow fuel tank mounting bolt and the frame full of fuel.

        Then there was A.J. with his GT car with the fuel tank with a mounting screw that controlled a bladder inside the tank. Nobody could figure how he got that great mileage with that BBC.

      • Thanks! It makes one hell of a racket too. When I first installed it the bike had the feeling of always being on downhill when I accelerated. Just a really positive feel.

        S&S V111

        • I’ve been eyeballing some of the Big Dogs and other S&S powered production choppers up for sale in the KC area. I just have a hard time with the idea of laying down 10 – 15 large for a scooter that is all about looks and attitude, but resides at the bottom of the performance and handling food chain when compared to my Z-1000. Although I must say that is one sweet looking engine on your scooter; fine job sir, fine job indeed! When I grow up, I want a hawg just like yours! 😉

          • This one ain’t a chopper, just an old ’96 Electra Glide on thin pizza cutter tires. It’s a pretty fun ride and holds it’s own with most production cruisers. It’s right at 1.8L 120hp and 120ft lb torque. I put a six speed over drive in it. It became a lot more fun after that! It’s like riding your most comfortable chair with a tractor engine.

  9. @Eric – Did you say 120HP on the Kaw? That is a lot of smoke for that machine. Should be a hoot from a rolling 60MPH start if nothing breaks. 🙂 That is late model Ninja territory.

    • Should be about that, yup!

      It’s punched out to 1015 CCs, has 10.75:1 compression and hotter cams, tuned exhaust/jetted carbs with pods and a V&H race-type header/can.

      It’ll roll!

      The first/lead pic is of my bike.

      • I’m not sure about a/c bikes, but with my a/c VW I went from a stock 1600 at 7.3-1 compression to a 2017 with 9.6-1, and it runs cooler (ambient temp has no effect on engine temp) with no extra cooling required (stock oil cooler), it’s all in the combo. You stated that you installed some hotter cams, you may need a little more duration (hold the intake valve open longer) to get your “effective” compression ratio closer to the stock static compression ratio. Your combo sounds pretty good, better flowing exhaust and the other things you did do help. More duration will move the power band up, but with the right port work on the head you will get some low end back (you don’t want the cam to out flow the head) It can be a juggling act, but that’s the part that makes performance fun, learning what works and what doesn’t. There are many calculators on the net to help determine your effective compression, I use Give it a try and see what you get. Is there any way you can set up some gauges (head and oil temp) to see some actual temps? I would assume that the two inner cylinders would run the hottest so that would be where I would put the head temp sensor (between the spark plug and the head). An A/F ratio meter would also be helpful to get your jetting dead on.

  10. Air cooled bike engines have been around a long time with a proven track record. If they were prone to failure we would have known it many years ago. Water cooled is more stable for lean mixtures, emissions, and parts longevity IMHO.

    Big horsepower outputs per / cc is risky business for air cooling. Just ask any Harley owner who has tried, and how much of a maintenance nightmare it creates. So big bikes like Harley & Victory use an oil cooler to help, but (I could be wrong but) all extreme racing Ninja bikes are water cooled.

    • Right you are, sir!

      I tried to make this distinction in the article. I’ve never had an issue with any of the (8) air cooled bikes I’ve owned…. in stock condition. I am more careful about riding the 900 Kaw, though. Because it has 10.75:1 CR pistons now and runs hotter than stock. I always use a high quality synthetic oil – and avoid idling in traffic on hot days especially.

      So long as you keep it moving….

      • If air cooled bikes are better then why do you need to “keep it moving” and use “synthetic”? Even Harleys now have an external oil cooler. Water cooled wins! ……by your own admission Eric.

        • Well, my bike is pretty seriously hopped up from stock. As I explained in the article, oil-cooled bikes are usually fine…. unless seriously modded for increased hp (and without adding oil capacity/an oil cooler, etc.) .

          So, it’s a balance.

          Air-cooled bikes have the advantage of being simpler – and less maintenance intensive.

          Water-cooled bikes have the advantage of being able to produce more power without overheating issues.

          • eric, I always enjoy stopping by the car wash on hot days and taking a break. Then aim the spot free rinse at it and eventually close in, wipe it down and wow, HP way back up. I have used a water/alcohol injection on autos to great advantage, let’s you run more timing and control when it begins to inject via throttle setting. You spend a lot of time in Tx. trying to figure a cooler engine. It’s one reason I love diesels in pickups. Sit there idling, cool and cool inside. Heat hasn’t been a big issue the last 3 months though…well, not overheat, lack of heat’s been a big deal.

  11. I’ve owned three air cooled bikes, a 1987? Suzuki Intruder 1400 and a 2000 Harley Ultra Classic Electraglide FLHTCUI and 2007 Yamaha Stratoliner 1800. The water cooled bikes were a 1983? Honda shadow and a 2003 Honda Silverwing. All bikes were awesome and well made performing flawlessly…..except the Harley, it was a turd and was in for repair most of the time. Air or water cooled depends on where you live in respect to sitting in traffic. Water cooled rocked as I never had to worry about overheating. My two cents.

  12. My air cooled Yamaha XS1100 Special didn’t even have an oil cooler yet it never overheated or incurred any heat related problems. Yes, it was ridden for many years in a big hot city with lots of traffic lights and long idle times. Excluding professional racing and antiques, I wonder if anyone can provide an example of an air cooled motorcycle engine stopping or being damaged due to excessive heat. I hope that Ken chimes in because he will undoubtedly know a hell of a lot more about this topic than I do.

    • If they’re stock – in my experience – you’ll almost always be ok (provided you don’t run it low on oil or leaned-out, of course).

      But up the CR two points, say, and then you may have issues – especially if you haven’t added an accessory cooler, etc.


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