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Liquid Vs Air cooling

Discussion in 'Bike Reviews, Questions and Suggestions' started by smidsy, Jul 26, 2009.

  1. Hei guys,
    Going to be buying a bike soon, a 250 road trail for some gentle trail riding and to get my license - I'm in WA so restricted to a 250.

    For what I want which would be lower speed stuff am I better going with air or liquid cooling.
    I know liquid is more complicated and probably more vulnerable if I put the bike down, but I'm also thinking it would be more tolerant of low speeds where there isn't the air flow.

  2. I think that air cooled engines have certain allowances to enable them to both run cooler and deal with the heat, including larger tolerances, lower state of tune, more airflow around the engine, that sort of thing. I had an aircooled parallel twin 500 and never had any issue with it on hot summer days in stop start traffic.
  3. From what I understand, air cooled engines aren't as tight - bigger tolerances to allow for higher operating temperatures.
    In turn water cooled engines have tighter tolerances and therefore are able to produce more power per cc and generally handle warmer working conditions better.

    My mates run 2 stroke 300cc water cooled KTM dirt bikes and Honda 250 CRF's and put them through quite a workout, this includes the odd tumble etc. They don't bust the cooling system everytime they go down - it would be an extremely expensive hobby for them if that were the case!
  4. Servicing costs can be somewhat higher for liquid cooled motors and it's generally quicker to service an air cooled bike (which is a consideration if you're doing your own servicing) but liquid cooled bikes tend to be more powerful (other things being equal).
  5. unless you are racing, air cooled is fine or even preferable.
  6. I'm not so sure about it being preferable.....money being no object, I can't think of a 250 single road/trail with a more economical, powerful or flexible engine than the wr250.

    It sure isn't aircooled :)
  7. The major advantage of liquid cooled engines is that the engine runs under a more stable operating environment. In turn, particularly for two strokes, this means a longer lasting engine.

    Ask anyone who runs air cooled 2 stroke dirt bikes how often they're stripping it down, giving it a rebore, or at best, cyl. hone and a new set of rings and piston.

    For a road bike there's no question as to which way you should go.

    After I migrated from aircooled 4 bangers to LC engines I have never had to pull one down for maintenance or overhaul.
  8. Some people prefer the aircooled as it simpler, one less thing to break if you drop your bike.

    You do lose HP for this simplicity though.

    Depends on your priorities
  9. Really? where does it go?
  10. Into the recycling with the coolant that you are dumping :)

  11. ooooooooookkkkkkkkkkkk
  12. Air or water cooled shouldnt factor into your decision, just go for the bike that ticks the right boxes. You won't get a high performance 250 with great brakes and suspension with an aircooled motor.
  13. Thanks for that guys - looks like liquid cooled is the way to go.
  14. I s'pose that if you're constantly dropping and breaking your bike then yeah, it is a valid point.

    As for being "simpler", LC engines are well designed. I've never had any problems with any of mine.

    As I said in another message it boils down (no pun intended - or maybe there was) to how often you need to rip the engine apart to repair it.
  15. The cooling method has little to do with maintenance life. Many of the latest water cooled four strokes need two-strokesch overhaul intervals.

    What drives this is their high state of tune, not their cooling method.
  16. I'd go a cheaper XR, KLR, DR, TT/XT air cooled 250 for the minimum period then upgrade to whatever floats your boat.
  17. What an extraordinary claim...
  18. why thank you.
  19. Erm.... they are interdependent, air vs liquid at the the equivalent (high) level of tune, liquid will the longer lasting more consistently performing engine.

    The move from air to water cooling is not some fashion trend, if engine makers could shave off the weight and cost of water cooling without a competitive loss, they would (and have in areas where performance does not matter beyond a certain point), how many cars are aircooled these days?, the only bikes that are aircooled these days are due to nostalgic or cost reasons and are not technically (output etc) competitive with their liquid cooled contemporaries.

    In just about any application (with the possible exception of aircraft engines), liquid cooling allows the design of a more efficient engine in regards to power, torque, emissions and economy, because the engineers are able to stabilize/bank on the operating temperature being with a certain range allowing finer tolerances in mechanical components, fueling and oil quality (as has been mentioned) .

    Name a performance piston engine that is aircooled.....(and not forced to be by class restrictions)
    gp bikes?

    The only exception I can think of, is top fuel drag cars, although their engines only run for short periods of time and are cooled by fuel.
  20. erm. . . yes it is.

    Water cooler on race engines is to do with sustained performance under race conditions. The stresses a bike sees during normal or even hard road riding is nothing like that witnessed by race engines. There is an order of magnitude difference.

    The trend towards street water cooled engines is largely marketing trading of race programs. So yes it is a fashion trend.

    The other factor influencing water cooling on production bikes is noise regulation. Water cooled engines tend to be quieter.

    But 80-90% of the reason for going to water cooling on motorbikes is marketing.

    Cars are a different story.