49cc vs. 66/80cc True or False?

Discussion in 'Motorized Bicycle General Discussion' started by Springfieldscooter, Jun 19, 2015.

  1. Springfieldscooter

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    True or False?

    Generally speaking, A 49cc accelerates quicker, and has a higher top speed than a 66/80cc engine?
     
  2. LandSpeedRecord

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    True, when the engine won't start.
     
  3. Davezilla

    Davezilla New Member

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    Yup... as long as the 66cc isn't running, the 49cc will be a bit quicker...
    Now if you're talking about a Morin 49cc compared to a China doll 66cc... ya... it's just a bit faster...
     
  4. fatdaddy

    fatdaddy New Member

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    I've ridden a few 49cc CG bikes. I cant say for sure that they don't wind out higher, but as for power, I find them lagging behind the 66/80 by quite a bit. The thing I've heard about them is they last longer because they don't have enough power to hurt itself. The 66/80 has enough power to pound itself to death if everything ain't perfect.
    fatdaddy.usflg
     
  5. crassius

    crassius Well-Known Member

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    I find the 49cc to be a bit faster on flat ground (but takes a while to get to that speed), but only the 66cc will get a heavy rider up a hill.
     
  6. Agreen

    Agreen Member

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    I have a 48cc china girl and I was seriously amazed at the power. I consistently get over 40 mph with it, and that's something I never got with the 66cc engine. A little less torque for powering up hills, but way it's a way smoother engine. I really do wonder how fast the 66cc would have gone if it was properly balanced and tuned.
     
  7. 2door

    2door Moderator
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    There is an old automotive saying that holds true for motorized bicycles as well.

    "The only substitute for cubic inches is, more cubic inches"

    There may be claims that the smaller engine has advantages and well they might. Nevertheless, power is a product of how much force is applied to the piston and when the same power is applied to a bigger piston, more power is the result when compared to the smaller one. All things being equal, the larger displacement engine makes more power.
    The key words here are "all things being equal". That is bike/rider weight, gearing, tire size, terrain and a host of other factores that must be taken into consideration when comparing smaller engines with bigger ones.

    As for vibration; the lower the crankshaft RPM, the less the vibration. But again, "All things being equal" plays into that equation as well.

    Tom
     
  8. Slogger

    Slogger Member

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    The CGs were all 50 cc for years and were designed to be that displacement.
    The carb, manifold, transfers and whatnot on a 66 are hand-me-downs. This seems to give it better low end but not quite the willingness to rev that the originals had.
    It's a fair trade, but it's too bad the 50s are disappearing. Everyone wants a 66.
    Bigger's usually better, so the 50s fade away.
     
  9. crassius

    crassius Well-Known Member

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    it's that 'all things being equal' part that gets you in trouble sometimes - not sure by how much, but 49cc piston is WAY lighter than 66cc - thinking it takes maybe a 1/4hp just to throw it up & down at 6000rpm - this may be why 49cc gets higher rpms on flat ground
     
  10. Greg58

    Greg58 Well-Known Member

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    I have built several 48cc engines that run well but they are not equal to a 66cc engine. The advantage the 48cc engine has is less vibration, my 48 is much more enjoyable to ride than my 66cc bike. Its probably due to the lighter piston, the balance is much better on a 48cc.
     
  11. dtv5403

    dtv5403 New Member

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    I am a bigger guy myself, standing over 6 ft and weighing over 18 stones. I do not own a kit bike, but have ridden both 48cc and 66cc kit bikes that were owned by my friends. I did not notice any difference in power whatsoever.
     
  12. 16v4nrbrgr

    16v4nrbrgr New Member

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    I guess the question to ask is; how do the 49cc engines stack up against the newer "balanced" 66cc kits in terms of high rpm vibration?
     
  13. Davezilla

    Davezilla New Member

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    I run the balanced Dax bottom ends in my builds and even at 10k rpm vibration isn't a problem at all... it's non existent at low rpm and barely noticeable at full speed.
    As far as power is concerned, the 66cc has a lot more torque down low, even when tuned and set up for speed.
     

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