First build, mtb

Discussion in 'Introduce Yourself' started by bAllah, Oct 26, 2011.

  1. bAllah

    bAllah New Member


    not mine, but its close, Ill get a real pic soon

    as far as propulsion, Im open to ideas


    looked at the honda gxh50,, but it's a bit out of price limit at the moment,,
    so im looking for a good deal on something around that topofthelegallimit power

    found this1, but only heard a few bad reviews

    then the knock off,,
    Im hoping its an entrepreneurial Chinese/American tradesman and not a scam,,,,


    anyone have experiances?? it looks way cooler than honda lawnmower engine knock off

    any suggestions on how 2stroke might b worth it? or why the 4 is beyond ease of fueling? seems like I could save alot on that engine

    also considering where the best place to mount the engine would be,,, and what kind of drive

    all I need is something that allows cargospace and unhampered bike riding, and that i can disengage when needed

  2. loquin

    loquin Active Member

    the blue max specs are below.

    You haven't listed your location, so it'll be tough to provide specific information...

    First. The displacement is 87cc. That puts it over the legal limit in many states (if not most states) for motorized bicycles. (Most states that allow motorized bikes have a 50cc upper limit. Some have a horsepower limit. Some have both.)

    You're putting the motor on a mountain bike; do you plan on keeping the knobby tires? If yes, that severely limits the use of a friction drive. It can be done; it's just not recommended...

    Keep this in mind... Your rear hub should be spinning at about 388 RPM to achieve 30MPH with a 26 inch bike. Divide the engine max RPM by the rear axle RPM to get an idea of the gear reduction you'll need.

    The blue max at 3600 RPM, divided by 388 RPM, would be ratio of 9.3. So, if you add a 10 tooth centrifugal clutch, you would need 93 teeth at the rear sprocket, or you would need to use a two-stage reduction (jackshaft or gearbox of some sort)

    The advantage of using the smaller, 30-49 cc engines with the built-in 78mm centrifugal clutch, is that gearboxes exist for these engines (So, even though they may have a higher max RPM, it can be easier to match the required wheel RPM to the engine power band.)

    Attached Files:

    Last edited: Oct 26, 2011