CVT CVT Adjustment nut

Discussion in 'Transmission / Drivetrain' started by Large Filipino, Apr 30, 2009.

  1. Just so it's here for those in the know,these CVT's are adjustable.
    Looking at the pic taken from that scooter site where I got mine you can see how you can adjust the spring tension. In the picture you see it adjusted inwards by looking at the gap between the chrome nut and the spring carrier.
    You'll need a thin wrench I used channel locks but you can ruin the thin nut get a thin wrench I don't know the size.
    Hold the nut with a socket and turn the thin nut clockwise if you want more tension on the spring and counter clockwise if you want less tension.
    I turned mine all the way counter clockwise for less tension and it improved my gearing quite a bit.
    Remember that my trike is unique as far as gearing and stuff goes so what worked for me may not work for you.
    This is just from what I learned today so please chime in but essentially if your belt is slipping then give that spring more tension and if you like to run your engine a little less rpm then give it less tension but not so much that your belt will start slipping.
    Mine isn't slipping so all the way out for me seems to work.
    Now that it's adjusted to what I think is right man does this thing haul to the point that I may need to lower my gearing by switching my 15 tooth jackshaft sprocket and look for a 16.
     

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    Last edited by a moderator: Apr 30, 2009

  2. Youngbird

    Youngbird Member

    So by running the nut out counterclockwise you allow the CVT to get to the top end sooner by having less tension on the spring? Are you going to look into changing the roller as well?
     
  3. Basically it gets to the higher gearing a bit sooner.
    My 15 tooth jackshaft sprocket while the CVT will still get me going without pedaling from a standing start won't take me to top gear and at that gear I'm literally flying.
    I don't remember but I think the sprocket on that 20 inch wheel is a 28 tooth.
    The 20 tooth I have laying around is already proven to me to be too low a gear so a 16 or even a 17 should do it.
    Sorry Youngbird. I don't follow when you ask about the roller.
     
  4. loquin

    loquin Active Member

    I don;t think that loosening that nut is a good thing to do, Large. I mentioned in the other thread that the total gearing needs to be based on the 3.2 to 1 reduction in the gearbox, and not on the 7:1 reduction under hi-load conditions. The total reduction after the CVT should be about 6.75 to 1... (assuming 25mph top end and 7000 engine rpm)

    Essentially, your gearing cannot be so high as to never let the CVT get out of the low range.

    What should happen is that the CVT allows the motor to get to it's best torque RPM, the bike picks up speed and the CVT gradually shifts the pulley sheaves. Eventually, the CVT will get to 1:1 at the pulleys, and the RPMs will then increase as the bike continues to pick up speed all the way up to the top end. If the rest of the gearing is too low (too 'tall') the bike can never get out of the low gear range. Since cronus had a 5:1 gearbox, the rest of the gearing didn't need to reduce the RPM as much. If you didn't change the other gearing, it would be about 36 percent too 'tall' for the CVT (at the same speed, that is).

    If you're running the bike with the wheel up, you're not getting a true representation of the bike operation under load.
     
    Last edited: Apr 30, 2009
  5. This is making more sense to me now. Thanks Loquin!

    It just seems to me though that loosening the tension made it shift up earlier but I understand why it wants to stay at 7 to 1 for so long.

    Gearing lower is the only answer here.
     
  6. Do NOT do this, unless you have another nut to lock it down.
    IT will open up on you and you will be left stranded.

    Best bet with the china cvts is add thin shims under the cap to raise tension,
    or cut the spring down for less. If you shim, use a very thin (width) washer
    so it just pushes on the spring, but the center pulley can still bottom out in the center of the spring's "cap"without hitting the shims.

    Every CVT has different spring tensions.
    It's amazing the difference in the consistency.
     
  7. The chrome nut is what holds everything down. That thin nut you cannot work it all the way out. It stops at the chrome nut. It actually turns with little effort and really just adjusts the tension on the spring.
    When this CVT wears in...naw. When I get this gearing down I'm gonna turn it in some but the way I got it it was turned in so much that it seemed to me the spring tension was too much but I also assume that turning that nut at its softest setting can't be good either.
    Anyway,if your belt is slipping,turning that nut clockwise can fix it.
     
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