Stock variator speed limit?

Discussion in 'General Scooter Discussion' started by m1tch, Nov 27, 2011.

  1. m1tch

    m1tch Member

    Messages:
    107
    Hi all,

    I am just researching my drag bike project a bit more, I have read the thread about why scooters can't go 90/100mph:

    http://www.scootershack.co.uk/threads/guide-why-scooters-dont-go-90-100mph.20337/

    The TDR drag scooters with their 172 engines run 11 second 1/4 miles with a terminal of 108mph, they are streamlined etc which means that they can reach the higher speeds.

    Thats not what I need to ask about though, the bike I am using for the project is a direct drive bike, so there is 1 drive sprocket and 1 driven sprocket meaning that there is a set ratio and a set top speed at X rpms.

    With the scooter CVT box the ratio changes which is why I am going with a scooter engine with a CVT as it means its simple but will mean I have 'gears' which is better than having a single set gear.

    My question is this, even if I have much more power coming from the engine, would the CVT box give a limit to its possible top speed owing to the fact that it will reach its top ratio in the box? If so what would it theoretically be? I have seen you can get 'gear up' kits which I am guessing makes the gearing longer, can you also get larger oversized variator pulleys or indeed make variator pulleys yourself (use an OEM pulley and extend the cone).

    The bike is for race only, it won't ever be used on the road, so unpractical solutions are fine :D

    Just wanted to ask as I am just working out where the restriction might be on the bike, I also find it quite funny how the stock engine zip 50cc is around 4bhp and my 37cc Blata engine is around 8 or 9.
     
    m1tch, Nov 27, 2011
    #1
  2. tErr0

    tErr0 Administrator Staff Member

    Messages:
    5,816
    The CVT only works up to a certain speed. Say 40mph. After that it goes to the gears which are just a simple set that run a ratio from the rear pully to the rear wheel. So all you have to do is fit higher ratio gears into the gear box which then gives you a higher top speed as long as you can pull that gearing with the power you have.
     
    tErr0, Nov 27, 2011
    #2
  3. m1tch

    m1tch Member

    Messages:
    107
    Ah ok gotcha, so the CVT basically gives you the acceleration and around town responsivness until it is maxxed out? When I saw there were replacement gearboxes for the zip 50 I got worried as I thought it might have been a manual or semi auto etc.

    I saw that you can get gear up kits for both the primary and secondary gears, would I need to buy them as a set or can I upgrade 1 or the other?
     
    m1tch, Nov 27, 2011
    #3
  4. nathan93

    nathan93 Moderator Staff Member

    Messages:
    760
    Rides:
    Gilera Ice
    you upgrade 1 or the other, 2 gear ups don't work together
     
    nathan93, Nov 27, 2011
    #4
  5. m1tch

    m1tch Member

    Messages:
    107
    Which one would be the best for top end? Power won't be an issue, just need to make sure that I can maximise all the power it will have etc.
     
    m1tch, Nov 28, 2011
    #5
  6. tErr0

    tErr0 Administrator Staff Member

    Messages:
    5,816
    You currently said you aren't going to fit a 70cc kit so you shouldn't be fitting a gear up kit.

    You buy either a primary or secondary gear up kit and work out the right ratio to give you the right percentage gearing increase for your added power.

    You should only ever fit a gear up kit when adding a lot more power. If you don't have the power to pull the longer gears you will just have slower acceleration and end up going the same speed.
     
    tErr0, Nov 28, 2011
    #6
  7. m1tch

    m1tch Member

    Messages:
    107
    Yep, im staying with 50cc at the moment, just working out my upgrade route for when I do decide to go with more power.
     
    m1tch, Nov 28, 2011
    #7

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