Scott started using water cooling in 1911, not '26. Mind you, they're pretty simple, AFAIK they are pure thermo-syphon with no pump, no thermostat and certainly no cooling fan!

The problem with aircooled engines is that the temperature varies due to variations in ambient temperature and use but more importantly, it varies across the engine. The cylinder head area runs the hottest but is also the most difficult to get the heat away from. In order to deal with these temperature variations some parts of the engine have to be carefully designed to avoid distortion caused by the differential expansion. In a watercooled engine the differential expansion is minimal, components can be made lighter and the engine can run a higher state of tune as heat dissapation is better. You should also get higher efficiency from watercooling as the tune (mixture/timing) can be set for a fixed engine temperature. Depending on the design watercooled engines are the one's more likely to overheat when stationary - especially enduro bikes which have the smallest possible radiator but even bikes with fans sometimes can't cope with high ambiant temperatures.

Aircooled engines should be designed such that they have sufficient fin area so they don't overheat when stationary for an extended period but this will obviosly depend on the ambiant air temperature as rate of heat transfer (which is fixed by fin area) is directly proportional to temperature difference. The crucial thing is if you leave you bike running in 40 degrees it will stabilise at a temperature 20 degrees higher than if the ambiant was 20 and does that 20 degrees extra cause the oil to start evapourating or breaking down - which in turn means oil changes and the correct grade (for the climate) are more important on aircooled bikes.

Simply, your fins are a heat sink.

Heat sink - Wikipedia, the free encyclopedia


They will still cool the engine while stationary but of course work better with air flow.

If you're engine is air cooled it will be because the engine will be able to take it with no issues. Low compression and low torque/HP engines don't produce enough heat for it to be a problem.

Although, didn't 'Lane Splitting' only become legal in some states of the U.S.A because those fat hogs were overheating in the summer while stuck in traffic ??

Urban legend ?

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

According to the AMA, lane splitting in California is neither legal nor illegal---there is no law regarding it. Police just let it happen.

Came across this zombie thread while browsing the site and thought I would add my 2p worth.

In my younger days I had a succession of cars (older models, admittedly) and every damn one seemed to have a problem with the water cooling. This made me glad of my a/c bikes and I even went to a/c for my car when I had a number of 2CVs, Dyanes etc. I used to regard water-cooling as the work of the devil.

Having said that, I have had plenty of water-cooled bikes in recent years, and not one has given a problem or even needed topping up between coolant changes. I am now completely confident in the concept, just like I am now happy with EFI. That took a while, too.

And having said that, if I were travelling right out in the sticks, I would probably choose the a/c XT over the w/c FGS, just because if it aint there, it can't go wrong.

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2006 XT660R daily ride, 1994 XT600E about to be reborn, Blog: http://goingfastgettingnowhere.blogspot.com/

You occasionally see window stickers on air-cooled VWs boasting of their 'infinite supply of free coolant'.

Having owned a number of VW's from the late-80s/early-90s, when they went over to water cooling, I sometimes think they got a bit stuck on this design philosophy, and didn't bother designing the system to actually keep the coolant in - you just keep pouring it in the top and it leaks out everywhere else.

(despite this I still own a wasserboxer T25)

And that my friend, IMO, is the most important thing when choosing an Overland bike. Simplicity !

Most of the "My bike is better than your bike" droll on here completely disregards this. Probably because the vast majority of hub members haven't quite got around to going anywhere yet, for whatever reason.

When you're half way down the road of bones or the bandit highway, how are you going to fix a leaking radiator or a BMW fuel pump solonoid actuater thingydoofer ? The AA doesn't want to know

Unless you know how to fix these things yourself and have the immediate means to do so, they are just things to add to the 'Things to go wrong and ruin your day/week/month list'

However, I'm not put off by watercooling on bikes. It's very simple and usually very reliable. You have to be pretty unlucky for anything to go wrong. The worst would be a cracked radiator and 'usually' they can be bodged up with Metal repair putty until you can find a welder.

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Did some trips.
Rode some bikes.
Fix them for a living.
Can't say anymore.

I'm lovin this, you've probably just made a few enemies though,HaHa
By the way my bike is definitely not better than yours

I've owned perhaps 20 different bikes, about half air-cooled, half water-cooled, and never had an issue with any of them overheating. With the air-cooled ones, if I was stuck somewhere in traffic and couldn't move, I'd kill the engine if the engine had to idle more than a few minutes.

I've never seen a problem with liquid-cooling on any of my bikes. Not to say it doesn't happen, but if I were planning a lengthy tour in a remote region, wondering whether I should have a liquid- or air-cooled bike wouldn't really enter into my decsion process on what bike to ride.

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Bruce Clarke - 2020 Yamaha XV250

The simplest old school bikes I own are the easiest to repair, but also the ones that need repairing and tuning the most often. I carry more spares and more tools on old school bikes than on modern ones.

On my bimmer all I carry is a waterpump kit and a subframe bolt, plus the usual suspects most of us carry (spare brake/clutch lever, fuses, consumeables, chain, etc, etc). Also, I only have to carry a small compact tool kit that doesn't see much use. Besides the regular services, the tool kit is hardly ever used for anything but checking for loose fasteners or taking care of flat tires. In fact, my f650gs has done close to 50.000 kms now and has seen zero brake downs. On my classic Vespa overlanding scooter on the other hand, I have to take half a scooter in spare parts and a huge tool kit... that gets used a lot as the bike seems to allways need something adjusted, serviced or repaired... but it is easy


In my opinion, modern (complex) bikes, with all its alloys, electronics, fuel management systems, hydraulics, water cooling, and so on, has over the last decades not only improved bike performance but also bike reliability. There is a reason for all this stuff, and it is not solely to get more power for less fuel and less nasty stuff in the air. Relaibility and less maintenance is also part of progress. And, as many of these "modern components" are in their millionth generation, the reliability of each component has also improved over time.

It is only natural that people get a bit uncomfortable with witch craft and the super natural... like electronics and micro chips. But, even electronics can be carried as spares or shipped in like any other part - much of it can even be mended or bypassed or have a part from a very different vehicle transplanted and adapted... like a water pump. More gadgety stuff may mean more stuff to trouble shoot if things go wrong - sure. But, modern is often more reliable as a whole in the first place, and hence, there will probably be no need to trouble shoot at all.

Sure there are stories of people in big trouble because a micro chip fried and died... but having a steering bearing racer brake, as happened to me in Zambia, is just as bad - some real old school stuff, that can't be mended or sourced anywhere, except through special order from Europe only. Four days searching in close to a hundred shops in the capital Lusaka left me no closer to a solution, my only solution was in the end to have a new part machined and adapted to my bike. If this had happened in a more remote place, even in Europe, I would have had to have the part shipped in, which really isn't a big deal anywhere.

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Blog: www.bamakobyvespa.no
My Youtube Channel

We've chosen air cooled over water cooled for the following reasons...
If a head gasket fails on a water cooled bike you are stuck usually with water in the oil. This is not good. The latest crop of Enduro bikes do not have the pedigree of either the XT600E or the DR650. Their frames are more flimsy and whilst Walter Colebatch proclaims the X-Challenge (which doesn't appear to be made anymore) is the perfect bike I am bemused by the number of failures/breakages he has had. My XT is doing approx 70mpg. My Ural Cross sidecar outfit, that I rode from Plymouth to cross Mongolia and return last year - unaided, was aircooled and did approx 39mpg even when loaded. The only problem I had with it was a cracked (from new) rear drive unit and the failure of the Slovakian built sidecar sub-frame. Yes the bike could be more energy efficient but at the cost of, in my opinion, simplicity.
I don't want ABS, fuel injection, turbo-charging, electric fuel pumps, or water-cooling.
If my carb blocks - I can repair it
If my headgasket fails - I'll get a bit of oil on my leg (by the way, I can repair it)
If my radiator punctures - Oh! Wait, I haven't got one.

It has been stated that the water cooling only adds 1.5kgs. Hah! Add the weight of this lot..
Radiator. the water in it, hoses and clips, thermostat, radiator fan, thermocouple to trigger the fan, electric fuel pump (which on the KTM adventure 990 takes 2 litres of space in the tank), A temperature sensor (to frighten the crap out of you when your engine overheats), perhaps a temperature guage... That lot weighs a damn sight more than 1.5kgs/3.3lbs.
Nope, I'm not a Luddite, I have all the latest tech at home and I will have GPS, a Netbook, 2 digital cameras, a mobile phone, and an air-cooled XT600 because I don't want to have to fix my water-pump in Siberia/Mongolia or wherever.
By the by, for all you Rotax engined riders out there, remember that the impeller that breaks inside the waterpump doesn't come with the repair kit! My friend Clyde got stuck in Aguinskoi (1 version of possible English spelling) for 21 days whilst BMW in America sent the impeller/s to him by Courier. He already had the repair kit. BMW in Moscow had the part but wouldn't send it as they said it would not get to him. That's why Clyde ordered it from the US of A.
I respect your decision to justify whatever bike you want to take and if it breaks down and I'm there I would happily help you repair it (I'm an Engineer). But don't lie to me about the advantages of taking a modern water-cooled, fuel injected bike.
I thank you
Andy

By the way, the XT600E has steel, chromed wheel rims. They are without a doubt the easiest rims I've ever changed tyres on, and that's why they're staying on the bike for next years travel - Bikers Abroad - Fools venturing forth on motorbikes

The thing is despite having all the electronic wizardry and water cooling you still have the possibility of a "steering bearing race" breaking.

Adding all the gizmos does not provide a cure for basic engineering faults. I had a big end bearing fail on a recent trip, but was able to continue for another 800 miles to park my bike somewhere safe until I could collect it. Generally electronic failures come without warning and are catastrophic (in that they render the vehicle unrideable) and unrepairable except by part replacement. Fixing my big end cost less than most engine management systems black box. The engine management system in my eyes is the ignition. so to have an ignition fault be more expensive than a crank failure seems ludicrous.

Andy,
I was wading through the rather usual , if not tedious (IIRC it's been done to death in the past), a/c V w/c arguments looking for some new angle when I arrived at the part of your post shown above; about an hour later after your posting number 26, I am somewhat surprised that you have not edited out the terminology "don't lie to me".
For clarity, who do you consider is lying in this thread?

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Dave

Andy, given the number of dishwasher repair men, machine operators and others who claim the title of engineer I’d suggest being more specific. For example in my case I would say I was a graduate manufacturing engineer working in process improvement as a six sigma black belt.

For Walkabout, a different answer:

I worked in the automotive industry for 13 years up to five years ago. My take on this would ignore the usual biker fixation with specific technologies. A Toyota Landcruiser (water cooled) will statistically prove more reliable in a long range travel environment than any bike. Sensible comparison though is close to impossible as comparable numbers just don’t exist. I would start my efforts on this by looking at:
· Intended use. If you exceed the design specification things will start to fail at an increasing rate. From the consumers point of view it is difficult to spot bikes actually designed for this type of use. Small capacity MX type machines are designed to race, so short , high power runs followed by any required maintenance, not carrying a lot of kit for a long distance. Larger machines may have off road style but are honestly expected to be used on sunny weekends and the odd two week holiday. Old machines may have had an expected design life that is now over, or the designer may have been useless and spent a fortune providing 40 year life parts for a 7 year life design.

· Design aspects that potentially detract from our requirement (electronic security systems etc.) I would say should count against a product. We need a cooling system though.

· Stability of design. Engineers, regardless of robust processes and taking the first point into account cannot find every issue until the product is used. Any new bike will have some sort of issue and the customers will find it. How this is dealt with varies with company culture, size and processes.

· Age of design and materials. We no longer see the sorts of obvious leaps and bounds they had in mechanical and electrical products even 30 years ago. What is changing rapidly is manufacturing techniques and materials. New designs can be more ambitious and without failures in their intended use because a component that used to be injection moulded and at risk of melting is now sintered ceramic. Things like 3D printing are going to allow shapes of component that were production impossibilities on older designs. These will be more robust and have higher performance.

· Where the design spec is met by sealed for life items, removing maintenance access is perfectly logical. Where this is not met, good design should make maintenance easy. Only where there are process failures will a semi-sealed design fail and require access.

· Robust process. The Japanese are the worlds best manufacturers. They have had detailed, naturally stable processes for almost every aspect of production for 60 years. A boutique manufacturer using non-automotive suppliers in small numbers cannot have the sort of process that simply does not make mistakes at any significant level. The root cause of the Ural subframe failure will almost certainly be related to a small production workshop relying on worker skill and inspection. Ural cannot insist the welding is done on a computer controlled process with statistical controls in place, the numbers are too small. Other manufacturers have adopted the Japanese techniques and some adapted them to other cultures but less experience still has an effect.


I therefore see no real argument in favour of either cooling system. A well executed water cooling system is more efficient. The well executed requirement is more likely to be a modern but proven design by a Japanese manufacturer or large manufacturer using Japanese techniques. Where the well executed design, working to an overland specification does not exist, air cooling can be meet many aspects of the requirement albeit at lower performance.


Basically, let someone with more money than sense do the testing on something fairly modern from a large manufacturer with a good reputation and don’t worry about what’s inside. Know how to fix what can be fixed and have the right tools , it isn't rocket science regardless.

Andy