Why did DS bikes quit air cooled

I look at DR350s that have no radiator and then the DR400s do. Just wanted to be schooled on why the move from air/oil cooled to radiated dual sport bikes. I see a Sherpa 250 in the for sale section sans radiator.

Doesn't the water pump and radiator add weight and complication to these bikes? What is the big benefit?

Water cooled is easier to make meet emission requirements.

Buffalo said:

Water cooled is easier to make meet emission requirements.

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I seem to remember that was part of why Harley developed the V-Rod. They needed a water cooled motor. At then time I remember reading that there were plans to require all street legal bikes be water cooled. At least I'm pretty sure that's what I read at the time, I've slept a lot since then.


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Tighter clearances available with water cooling let the engineers get more power from a given displacement. They can set higher compression levels reliably, set cam lift and timing a bit more aggressively, and usually design the whole package for higher RPM function.

The DRZ 400 makes considerably more power than the old DR 350. My Yamaha 250 has much more the power than my old air cooled XR 250. Same displacement, both have 4 valves, yet there are ten more ponies available with the water cooled machine. For most street riders a ten horse difference might not sound like much. When you consider the percentage difference going from 14 horses to 24 horses, it is a leap.

I thought there might be some advantage in extreme low speed high load on rough trails from overheating but the 14 to 24hp is going to be felt on the road and trail.

Air cooled - 2 stroke; life just doesn't get much simpler.

jbird710 said:

Air cooled - 2 stroke; life just doesn't get much simpler.

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Or dirtier.

SL350 said:

I thought there might be some advantage in extreme low speed high load on rough trails from overheating but the 14 to 24hp is going to be felt on the road and trail.

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Not with a properly designed system. My WR450 which was notorious for running hot when the trail speed dropped would boil coolant into the catch can almost every time on rough trails. As soon as I got moving again it would cool down enough to slurp it back in.

For sure, there is a downside in that you now have more parts to break. I cracked a radiator when a strap holding the bike to the trailer came loose a little bit and went under the wheel of the moving trailer. I've seen a radiator get torn open when a rider slid down a very rocky and nasty hill. And I've seen a few cracked water pumps in my trail riding days.

But I also have a 250cc water-cooled two-stroke that makes every bit of 40hp but weighs just over 210lbs. I wouldn't trade that for the world.

KenH said:

Or dirtier.

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Not if tuned properly.

Is there a dual sport two stroke? One that can do the pavement at 65? Thought two strokes on the street were a thing of the past.

ed29 said:

Tighter clearances available with water cooling let the engineers get more power from a given displacement. They can set higher compression levels reliably, set cam lift and timing a bit more aggressively, and usually design the whole package for higher RPM function.

The DRZ 400 makes considerably more power than the old DR 350. My Yamaha 250 has much more the power than my old air cooled XR 250. Same displacement, both have 4 valves, yet there are ten more ponies available with the water cooled machine. For most street riders a ten horse difference might not sound like much. When you consider the percentage difference going from 14 horses to 24 horses, it is a leap.

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^^Yup^^

SL350 said:

Is there a dual sport two stroke? One that can do the pavement at 65? Thought two strokes on the street were a thing of the past.

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Not that I know of. The 6-speed KTM's would be about as close as you would get but I'd bet good money that they aren't very happy holding a sustained 65 on an interstate. Those days ended right about the time that two-strokes started getting power valves.

Honestly, for dual sport riding today I would be hard pressed to look further than the WR250's. They don't have a ton of power and are a little portly, but they just run forever and you never have to mess with them.

SL350 said:

Is there a dual sport two stroke? One that can do the pavement at 65? Thought two strokes on the street were a thing of the past.

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I still see a few plated. Running one at 65 with stock gearing might be a stretch. I'm sure they can hit 65 but I sure wouldn't stay there long.

SL350 said:

Is there a dual sport two stroke? One that can do the pavement at 65? Thought two strokes on the street were a thing of the past.

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I was over ogling the new Freeride at Wild West (and no, they didn't ask if I needed help this time, either) and noticed a sticker on the back that said something like "For closed circuit use only. Not for trail or street use." I assume this is to satisfy the CARB Red/Green sticker program, or at least let potential buyers know that they may be limited in where it can be ridden.

In Texas it seems anyone can plate anything with two wheels if they can somehow get it to a lax inspector. For the time being anyone wanting a 2 stroke DS bike will have to make one. I bet JMZ's KTM 300 will hit 65.

Two Stroke Resurrection

Boy we're all up early for a Sunday.

One other thought. I really considered a 2 stroke DS for the LAB2V type riding, but couldn't get past the fuel problem. Sure, I can mix gas and oil at the pump with the best of them, but man are those things thirsty. I couldn't find one with an aftermarket tank that was up to 150 miles of riding. Anybody know of one?

Meriden said:

Boy we're all up early for a Sunday.

One other thought. I really considered a 2 stroke DS for the LAB2V type riding, but couldn't get past the fuel problem. Sure, I can mix gas and oil at the pump with the best of them, but man are those things thirsty. I couldn't find one with an aftermarket tank that was up to 150 miles of riding. Anybody know of one?

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Too early!

You're right about mixing fuels and they do suck it down. And vibration!

When in Co. I did see these 2 for sale, but as you can tell, they are really only trail worthy.

SL350 said:

Is there a dual sport two stroke? One that can do the pavement at 65? Thought two strokes on the street were a thing of the past.

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I have a new copy of "What Bike?", a British motorcycle magazine. It lists this years bikes for sale in Britain. There's a bunch of little air cooled two strokes road bikes for the lowest class license. They live, just not here.

I had a Maico 501 that would do 65mph all day long, or until running out of gas, whichever came first. 17mpg while desert racing. Usually about 35mpg when cruising along ranch roads at sane and safe speeds.

Stock 501s were fitted with a weak clutch so were detuned to about 35hp. The 400, 440, and 490 versions were all faster on a motocross track, but were tuned too hot for desert play riding. Some of the better combinations with forward shocks or the last of the monoshocks will still run with the latest and greatest. They were the only things that could give the CRs a run for their money back then.

Fit the stronger clutch and start tweeking. Have a strong grip for stopping, but even when played with a 60hp 501 was a torque monster if done right so the clutch on mine was rarely used. 501s tuned to the max dynoed 75-80hp.

A stock 501 would run all day at 80mph because it was one of those engines choked down so that even at full throttle it was only running half throttle. The stronger clutch, bolt ons, port work, and carb jetting would make a 50hp stump puller pretty easily with about 100mph top end. Mine was tweeked to about 60hp and would run about 115mph, ridden next to I40 in the desert, clocked by a state police car. The maxed out monsters would run about 125, but I've heard at 12.5mpg or so while racing.

So, if I really wanted a 2-stroke dual sport for some type of adventure riding, I'd go with a 501 reworked with a wide ratio 5 speed trans (the originals were 3 speed, later models had 4), modded to the 50-55hp range, dropped in a late forward twin shock or monoshock frame (the early monoshocks were junk, so a good source of engines), fitted with the early enduro electrics, and somehow figure out how to carry 12 gallons of gasoline.

The Yamaha 360 comes to mind. Jetted a bit rich I expect 65mph all day would be easy.

KenH said:

The Yamaha 360 comes to mind. Jetted a bit rich I expect 65mph all day would be easy.

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That one came to my mind too, it and its 400 brother. And that was BEFORE big gas tanks. There was an ADV ride a few years back with several guys doing portions of the TAT.

SL350 said:

That one came to my mind too, it and its 400 brother. And that was BEFORE big gas tanks. There was an ADV ride a few years back with several guys doing portions of the TAT.

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More fuel is easy to carry. Stock tanks can be reworked or replaced. Auxiliary tank above carb intake level will gravity feed, though a pump or pouring will be necessary to transfer to a gravity feed tank if a lower location is chosen. Replacement and auxiliary tanks intended for other models might fit.

My TW200 for adventuring carries about 12 gallons, 4 in a XT600 replacement from Clarke, 4 in a custom auxiliary under the luggage rack, 2 in a custom auxiliary behind the headlight, and 2 in an auxiliary between the side bag rack and swing arm. How creative are you is all that matters.

I blame Al Gore for the scarcity of air cooled bikes. He invented global warming which caused air temperatures to raise and subsequently be too high for proper air cooling. People still rode those air cooled bikes as they didn't know for the better but then Al Gore went and invented the internet so everybody became knowledgeable about the cooling deficiency and stopped buying the bikes.

KenH said:

...My TW200 for adventuring carries about 12 gallons, 4 in a XT600 replacement from Clarke, 4 in a custom auxiliary under the luggage rack, 2 in a custom auxiliary behind the headlight, and 2 in an auxiliary between the side bag rack and swing are.

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Holy Batman! 12 gals? TW gets what 50mpg so fuel range of 600 miles? I don't think there is a place on earth that doesn't have gas at 300 mile intervals is there?

_

One aspect of this issue that has been touched on is that ALL motorcycles (and ALL cars) are air-cooled. Period. Some of the heat produced in the combustion chambers may be transferred by liquid to a radiator, but in the end, air does the cooling. And unfortunately, a radiator (really a convector), doesn't work efficiently unless it has air moving over it with some speed. I think Maico had the right idea - big cooling fins on the cylinder and head. A simple and 100% reliable way of getting rid of excess heat.

DFW_Warrior said:

Not that I know of. The 6-speed KTM's would be about as close as you would get but I'd bet good money that they aren't very happy holding a sustained 65 on an interstate.

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The wide ratio KTM two strokes could hold 70 mph on the interstate all the way across the entire country. Most of the ones I ride with are 300cc xcw's, and they purr down the road at 65 mph. Why would they not? It is simply a matter of gearing and power, and the 6th gear that KTM installs in the XCW is very tall. Top speed on a newer 300 xcw is close to 90 mph.

Now, they might not be comfortable for long periods, but they cruise down the highway with no problem. Seen it myself many times over.

Johnf3 said:

The wide ratio KTM two strokes could hold 70 mph on the interstate all the way across the entire country. Most of the ones I ride with are 300cc xcw's, and they purr down the road at 65 mph. Why would they not? It is simply a matter of gearing and power, and the 6th gear that KTM installs in the XCW is very tall. Top speed on a newer 300 xcw is close to 90 mph.



Now, they might not be comfortable for long periods, but they cruise down the highway with no problem. Seen it myself many times over.

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That is good to know. I've only ever ridden the XC-W's up at Red River and 6th gear doesn't ever happen up there. LOL