engine size, size does matter

Discussion in 'General Questions' started by bobby-brazil, Aug 11, 2009.

  1. bobby-brazil

    bobby-brazil New Member

    ok now that i have your attention, are the exterior dimentions the same between the 80 cc (60) and the 49 cc engines? or is the 49 cc smaller?
     

  2. rockvoice

    rockvoice Member

    the case appears to be the same size, but the head , cylinder are noticebly larger
     
  3. bobby-brazil

    bobby-brazil New Member

    thank you both very much
     
  4. Top Cheese

    Top Cheese New Member

    How much difference in speed is there in the different size engines. Because I'm pretty sure I have a 80cc and I topped it out at 26 on a straight away. With a CNS carburetor, and a 36T sprocket. What's up with that?
     
    Last edited: Aug 12, 2009
  5. speed also depends on how much you weigh.
    i weigh 120lbs and i have a 48cc(stock parts) with 44t sprocket and can hit 30-32+mph.
    it will go faster after breakin.

    btw both size engines go about the same speed. it just the larger engine can pull more weight.
     
  6. Top Cheese

    Top Cheese New Member

    I way 140 with a cns carburetor on it. and I let her loose only at 27.7mph today. There is about 120 miles on it. What am I doing wrong?
     
  7. your engine is still in break-in,after break-in it will go faster, trust me.
    mine would do 26-28mph during breakin and now goes 30-32mph.
     
  8. Top Cheese

    Top Cheese New Member

    When will it be officially done with break in? Millage wise? And I have a 36T would a 44 be faster?
     
  9. motorpsycho

    motorpsycho Active Member

    I have the 49 c.c. slant head engine, mounted on a 20" frame with 20" wheels, and a 44 tooth sprocket. the motor is all stock except for a custom made carb stack and it has about 10-15 miles on it. i weigh 155 lbs, and i am getting 22-25 mph top speed. (it's not broken in yet so i am hoping the top speed will increase a little once it gets broken in)
    I'm not sure how much difference it makes on your wheel size (like will a 26" wheel give you higher top speeds than a 20" wheel?)
    my friend has an 80 c.c. on a 24" frame, with 20" wheels and a 44 tooth sprocket. he weighs more than me but our top speeds are identical. the 80 c.c. has more torque and faster take off than the 49 c.c. but i can catch up to him and stay side by side with him.
    he has an i-phone with a speedometer on it (and it is accurate) and that's how we measured the speed.
     
  10. motorpsycho

    motorpsycho Active Member


    no, the smaller the rear sprocket is, the higher your top speed will be. a 44 tooth will take away some of your top speed, but it will give you more bottom end torque for better take off...it will be easier for the motor to get your bike moving.
    if you want really good take off, go with a bigger sprocket, (44, 48, 56) if you want more top speed, go with a smaller sprocket (41 or 36 not sure if there is a smaller sprocket that 36 but someone probably makes one).
    you can't really have excellent take off AND really high top speeds with a stock motor...it's one or the other. i think the 44 tooth sprocket is kind of the middle of the road sprocket that gives you good take off, with decent top speed.
     
  11. BAM

    BAM Member

    80cc broke in 44 tooth 33mph but motor was screaming swhinn speedo waiting for piston to come flying though my leg thats why i would like to try 40 tooth but hate to mess with the bike 800 miles with no promplems yet! 20 to 1 gas
     
  12. Top Cheese

    Top Cheese New Member

    What is a good break in oil to gas ratio?
     
  13. give me vtec

    give me vtec Active Member

    16:1 after about a gallon, start working your way to 20:1 - 25:1

    before you start the engine... pull the spark plug out and squirt a little oil in the hole. Then cycle the engine through a few times w/out the spark plug connected to the cdi. You can either do this by removing the clutch lever/sprocket cover and manually rotating the engine with a socket wrench. Or if the engine is hooked up to the chain and rear wheel just roll the bike forwards a couple of yards.
     
    Last edited: Aug 12, 2009
  14. Top Cheese

    Top Cheese New Member

    Also what type of gas should I be using?
     
  15. give me vtec

    give me vtec Active Member

    regular pump gas...
     
  16. mattysids

    mattysids Member

    adding to vtec, remember that higher octane is not better. higher octane gasoline is used in really nice cars because it is actually HARDER to burn, and this quality prevents their high compression ratio engines from knocking. These engines are "designed":jester: to burn very simple fuel.
     
  17. Top Cheese

    Top Cheese New Member

    Any certain number? Like 89 or anything?
     
  18. mattysids

    mattysids Member

    the lowest one at the pump so yes
    89 is appropriate
     
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