Horsepower, RPM, speed?

Discussion in 'General Questions' started by JVROOM, Oct 14, 2012.


    JVROOM Member

    Okay here's a question, still working on this project 66cc/head. Jaguar CDI, upgraded carb, expansion chamber, waiting for reed valve kit. Engine sprocket 10, wheel sprocket 44. Plugging it into the Calc chart shows 61.5 miles an hour at 3500 RPMs. No way that's going to happen, horsepower isn't there. With a 66 wheel sprocket, at 3500 RPMs Calc shows 41 mi./h, doubtful if that would even happen, don't want to go that fast anyway too dangerous.

    So the question is with the typical 44 rear sprocket are these engines bogging down, in other words should they be spinning up a little faster, or to say that another way does anybody know what the ideal RPM range is for these typical Chinese engines.

    Wondering if the RPM range is too low, and the engine is just bogging down and running at zero vacuum? Thanks for everyone's thoughts sincerely, John :-/:bowdown::confused::detective:

  2. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    Your engine is spinning at 3,500 rpm

    Then there is a 20 tooth gear driving a 82 tooth gear.

    Then there is a 10 tooth sprocket driving a 44 tooth sprocket.

    That will give you a speed of 15 mph with a 26" diameter wheel.

    JVROOM Member

    Okay, I missed something here that big way? I was using a the gear ratio chart I found here on the forum, it had a one-to-one ratio listed to I need to change that for the 20 to 82, is that like for the one? Thanks for your help
  4. MotorBicycleRacing

    MotorBicycleRacing Well-Known Member

    The 3 boxes should look like this.




    JVROOM Member

    Okay I'm missing something here, I was using the gear ratio calculator chart found on the forum? Let's see it has a one-to-one ratio would I need to change that for the 20 and 82 gears to something like 4.1? As you can see learning all play with that little bit thank you

    JVROOM Member

    Okay, thank you very very much, no I'm not really brain-dead, just didn't think about that. So with the 44 sprocket 20 mph would be pushing it, I guess I could go to the 36 sprocket, but there's a lot of hills around here so, probably better off just leave well enough alone. In 20 mph is fast enough. Again thank you for educating me, sincerely, John