How to tell the difference between 49 and 66cc?

Discussion in 'Motorized Bicycle General Discussion' started by fischer550, Mar 24, 2014.

  1. fischer550

    fischer550 Member

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    Hey guys, I just got a motorized bike engine and I do not know if it is 49 or 66cc. Is there a way I can tell without taking it apart (head nut size for instance)? Also, I heard that to take the engine head off, I need a tool called a torque wrench. Is this right, or can I use a regular socket wrench? Thanks
     
  2. needtransportation

    needtransportation New Member

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    I cant help you with how to know the difference between sizes but you DO NOT need a torque wrench to take it off. A torque wrench measures how much force you are applying while tightening to ensure that things are tight enough to to stay together but not tight enough to break bolts. It is for tightening bolts and you can live without it if you are experienced with the feel
     
  3. Theon

    Theon New Member

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    49cc more likely will have 6mm head studs, 66 more likely 8mm head studs.
    but this may not be a golden rule. there is a slight difference in head stud spacing also, the 66 has 45mm centre to centre head stud spacing, not sure of the 49, but it's less.
     
  4. fischer550

    fischer550 Member

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    OK, so I have just decided to make sure so I took the head off, so now what do I measure to determine the displacement?
     
  5. Theon

    Theon New Member

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    66cc will have a 47mm piston/bore, 49cc is a 40mm piston.
    there is also a 45mm piston, but quite rare.
     
  6. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

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    You do not need to remove the head to tell the engine size.
    Does your motor have 6mm or 8 mm head studs?
    If they are 8mm it is a 66cc
    48cc have flat top pistons while 66cc are domed.
     
  7. Kioshk

    Kioshk Active Member

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    OK, now put it back on!
     
  8. Matheneyr3

    Matheneyr3 Member

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    Careful Partner- Read and search- Lots of great info on this forum. Experiment @ your own risk.
     
  9. mapbike

    mapbike Active Member

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    I have an old 2009 model 66cc engine that has 6mm studs 47mm bore and also has a smaller bolt pattern for jug/head, it also has a flat top piston and a straight plug head that has a much smaller combustion chamber, it was a Boygofast motor that was labeled as a Red Bat Engine, probably not to many of those still out there but it is an odd ball compared to the 66cc engine we have now, it has been an excellent engine as far as longevity, but it will vibrate your socks off at higher rpms.....lol

    Measure the bore and you'll know 100% what you have but most likely if it has 6mm studs it is likely to be a 49cc and 8mm being most likelya 66c, qgain measuring the bore is the best way to be certain.

    Map
    Peace
     
    #9 mapbike, Mar 25, 2014
    Last edited: Mar 25, 2014
  10. vhatley

    vhatley Member

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    AoSom has the rare 60cc...thought I was the only one who knew bout that...and don't trust their online specs...It's a 66cc low-end. The crank, rod, bearings, ****, even the magneto and clutch components are all 66cc. JUST the actual crankcase is fit to a jug that is the 45mm spec.

    These ALWAYS HAVE THE 6MM stud size and a plug in the center of he domed head...ALMOST a HEMI :D:D
     

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