vintage liquid versus air cooled engines

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cleopatrisha

Member
Dec 16, 2006
86
0
Any advantages disadvantages to air or liquid cooled engines?and do liquid engines really last any longer?
 
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CRazy250

Member
May 28, 2006
334
1
liquid cooled are less prone to overheat unless you have a leak someplace in the cooling system, aircooled seem to have more power i think because they dont have to spin a waterpump......but i do love the simplicity of a aircooled engine. either way they work good and do the job.
 
Y

Yz250JdT250

Member
Apr 26, 2004
142
0
Are the old liquid cooled motors counterbalanced? I had a 1982 yz250j and it was maybe as fast as a modern 125. BUT all i did was rebuild the top end becuase compression was low around 90 psi, no porting or anything. I think it probably needed a complete rebuild anyway. On the other hand, i also have a 1977 DT250 (air cooled) and it runs like a champ!
 
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Bultaco206

Member
Aug 19, 2003
39
0
I have an article somewhere (MXA I believe) where they were doing a test on the new '81 CR250. It was quoted that Honda had proof that the '80 CR (last air-cooled) lost up to 20% of its power late in the race due to excess heat - and felt that liquid cooling gave them a way to disperse it so the power decrease wouldn't be a factor. (It's not that the bikes ran any cooler - it was a way to disperse the heat more efficently.)

It's my opinion that bikes with steel liners run cooler than chrome bores anyway. There must be some truth to that as Honda went back to steel liners in it's first two generations of water-cooled bikes. (My '83 is steel-lined & liquid-cooled.)

I'm also a big believer in that anything you leave off a bike can't break...and prefer air-cooled bikes.
 
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thorman75

"Team Army"
Member
Dec 9, 1999
673
0
Honda said the engine had lost over 20% of its power late in the race, I myself on the other hand have lost 95% of my strength by the time the white flag comes out so it dosen't really matter.
 
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Bultaco206

Member
Aug 19, 2003
39
0
thorman75 said:
Honda said the engine had lost over 20% of its power late in the race, I myself on the other hand have lost 95% of my strength by the time the white flag comes out so it dosen't really matter.
Click to expand...

What kind of liquid are you running? :)
 
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thorman75

"Team Army"
Member
Dec 9, 1999
673
0
Mostly MGD.
The Maico dosent like it, it naturally prefers Becks(Dark/ Warm)
 
C

CommandoRoadster

Member
Nov 21, 2006
37
0
All else being equal a liquid cooled bike will put out power consistantly over a longer period of time than an air cooled bike,which loses some power as temperature rises.This is more evident on small bore two strokes.Since more heat equals more friction, and more friction equals more wear, theoretically liquid cooled engines will have a longer lifespan than air cooled engines.

An all alloy cylinder will dissipate heat more efficiantly than one with an iron liner. The reason they went back to liners was so you could re-bore the cylinder, instead of having to buy a new one.

I'll take an air cooled bike any day, myself. :)
 
2

2 strokes for life

Member
Jan 3, 2007
1,860
0
I have a 1979 Yamaha IT175 (air cooled). It works well on the track and woods. It has not needed a rebuild yet (since factory). I think i will do one thoe. Looking to buy liquid cooled bike this up and coming summer.
 

BadgerMan

Mi. Trail Riders
Jan 1, 2001
2,479
10
cleopatrisha said:
Any advantages disadvantages to air or liquid cooled engines?and do liquid engines really last any longer?
Click to expand...

More consistent cooling (liquid) means that internal tolerances can be tighter since thermal expansion is more controlled and less of a factor than for an air cooled engine......or so I have been told.

Personally, I think liquid cooling is one of the best things since sliced bread. :cool:
 
W

wirefryer#85

Member
May 26, 2006
158
0
Liquid cooling eliminates a huge variable in engine tuning, temperature.

The more variables your can eliminate or negate, the easier it is to get to optimum benifit from the things you can easily change, like carb or timing settings.

I love air-cooled bikes, but run them hard in sand or tacky soil and you'll feel the engine get soft on you. Once it cools down a bit the power comes back.

But I never have to think about wasting a $400 radiator if I gotta drop it in the rocks :) .
 
2

2 strokes for life

Member
Jan 3, 2007
1,860
0
I ride my air cooled bike in the sand mostly and i dont notice anything at all. So, you are saying i will have more power in the sand with a liquid cooled bike.
 
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CommandoRoadster

Member
Nov 21, 2006
37
0
wirefryer#85 said:
But I never have to think about wasting a $400 radiator if I gotta drop it in the rocks :) .
Click to expand...
Amen,wirefyer,Amen

2 strokes for life said:
I ride my air cooled bike in the sand mostly and i dont notice anything at all. So, you are saying i will have more power in the sand with a liquid cooled bike.
Click to expand...
When you get that liquid cooled YZ you'll have lots more power. You bet!
:nod:
 
2

2 strokes for life

Member
Jan 3, 2007
1,860
0
The YZ looks good but i am now converted to scary fast power like my uncles YZ490. Wich of all the 250s have this scary power i seek.
 
M

MX86

Member
Dec 27, 2006
214
0
None of the bikes will come close to the yz490.. polished and ported maybe. The yz490, WR500, CR500 are kings of displacement.
 
P

pokemanyz

Member
Jan 22, 2000
41
0
thorman75 said:
Honda said the engine had lost over 20% of its power late in the race, I myself on the other hand have lost 95% of my strength by the time the white flag comes out so it dosen't really matter.
Click to expand...

I used to race Friday night MX at the stock car track in Crown Point back in the 70's
Mark Barnett designed the track, may have been his first?

I wonder what happened to the MX track. I see the stockcar track is still there.
 
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CommandoRoadster

Member
Nov 21, 2006
37
0
That Service Honda goes for about $9000.00 doesn't it? You could probably get a YZ490 for about $1000.00. They weren't very highly rated by the magazines. Great playbike, but bad racer, supposedly.I had a YZ400E and I loved it.It was the fastest bike around, back then.Till my friend got a 450 Maico........ :yell:

Hey, a guy at work is looking at buying a '83 CR125(God knows why, he has a YZ400, and an '83 Maico 250) that needs a stator, a rotor, and a CDI module. Any body got that stuff they want to get rid of?
 
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thorman75

"Team Army"
Member
Dec 9, 1999
673
0
Are you sure Mark designed the track. If he did I dont remember that. ( he would have been awful young to be designing tracks, if I remember next time I talk to him I'll ask)
I raced most of the tracks around here, K&R, Red Bud, Hawthorne, St Anne, etc.
 
2

2strokerfun

Member
May 19, 2006
1,500
1
BadgerMan said:
More consistent cooling (liquid) means that internal tolerances can be tighter since thermal expansion is more controlled and less of a factor than for an air cooled engine......or so I have been told.
Click to expand...

If I remember correctly from internal combustion classes in the late '70s, a liquid cooled engine is--on average--11 percent more efficient than air cooled due to this very reason.
At least that is what we were told and it does make sense although the number might be wrong.
 
2

2 strokes for life

Member
Jan 3, 2007
1,860
0
My uncle has now found a IT465 that has been baord so much that it mealts a piston every time he rides it. I think it is boared 3 or 4 times over. New cylinder head.
 
2

2 strokes for life

Member
Jan 3, 2007
1,860
0
I think the KTM300 with a SX300 flywheel and ignition should give it a good kick in the pants. Also, L.A. sleeve makes a YZ330 kit wich looks really good.
 
J

john221ex

Member
May 1, 2006
35
0
cooling

Water cooling on a motorcycle is purely a marketing ploy.
The manufacturers get to sell you more parts and the shops sell you more service.
Who, besides the top 15 or 20 pros in the world can work a bike hard enough to use that alleged cooling advantage?
I would remind you that Porsche won LeMans many times with air-cooled engines and they only went to it for the same marketing reasons as bike manufacturers.
Also noteworthy is that one of the most durable motorcycles still retains air cooling: BMW.
I rode for years in desert races and even there, never had any heat issues with any of my bikes.

John
 

BadgerMan

Mi. Trail Riders
Jan 1, 2001
2,479
10
john221ex said:
Water cooling on a motorcycle is purely a marketing ploy.
The manufacturers get to sell you more parts and the shops sell you more service.
Click to expand...

Now that's funny right there!

If you factor in the rate of inflation, you are spending much less on top end rebuilds for a modern bike than you did in say the mid seventies.
 
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