CVT Full Suspension CVT

Discussion in 'Transmission / Drivetrain' started by kerf, Oct 11, 2010.

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  1. kerf

    kerf Guest

    Having finished my latest incarnation of the Snake Eater and having put about 60 miles on it, I can absolutely say I no longer have an MB. This thing has crossed the line to moped or motorcycle or something. Never in all my builds, have I ever had this combination of hill climbing ability and super cruise. Guess I may get booted off the forum for good.

    For this build, I wanted speed, power, quite and a smooth vibration free ride. To that end, I used the CVT rubber mounts and added rubber isolators at all other mounting points. The power is routed from the CVT through a 14 tooth sprocket, down to a 72 tooth freewheel sprocket on the wheel. The chain is 8MM, which seemed to be the easiest way to go. I bought a scooter muffler but wasn't happy with the chain saw sound. I gutted the muffler, added about 4" of length to the housing and created a straight through glass pack, with a spiral baffle inside the the core tube. Since I had been running a Staton chain drive, my Staton rear hub had a 16 tooth left hand freewheel. I just pulled down the bottom bracket and swapped the pedal chain to the left side. A quick idler roller and it works like factory, single speed of course.

    I'm still playing with gear ratios, to find the optimum and I ordered an 11 tooth trans. sprocket this morning. The story of gear ratios goes like this, my old Staton box was geared at 18.75:1 and my chain drive was 1:1, giving me a final drive ratio of 18.75:1 and it let the R460 breathe real good. Before the build I checked the CVT and found the gear box was 3.71:1 and the belt was 1.89:1 in low range, giving me a 7.0:1 total in low range. I could only estimate the belt in high range and I thought 1:1 looked pretty close, giving me a total of 3.71:1 in high range. I just clocked the bike at 35 MPH and it was turning 6550 RPM, so backing into the numbers, the belt looks to be closer to .775:1 in high. That makes a huge difference.

    Here are the final ratios available to me:

    Trans. high range 2.875:1 - chain 14/72 = 14.79:1 final. (running that now)

    The 11 tooth trans. sprocket will make this available.

    Trans. high range 2.875:1 - chain 11/72 = 18.82:1 final.

    Trans. high range 2.875:1 - chain 11/63 = 16.47:1 final.

    Man, what a rush!

    Attached Files:

    Last edited by a moderator: Oct 11, 2010

  2. professor

    professor Active Member

    You sure do nice work Kerf. Looks factory.
  3. kerf

    kerf Guest

    Thanks professor. This thing has been in my head for more than three years. I even bought a transmission several years ago and finally returned it because of technical issues. It was TREEWK that put me on the right track with his build.
    Post #86

    About 4 months ago, I bought another trans. and began accumulating materials and parts. Finally I had the time and just decided to take the plunge. Had to ride the wife's bike for a couple of weeks but it all worked out.
  4. eastwoodo4

    eastwoodo4 Member

    nice job.would love to take it for a ride.
  5. Turtle Tedd

    Turtle Tedd Member

  6. GearNut

    GearNut Active Member

    Very well done indeed! I like your attention to detail, and the bass ackwards pedal system.
    What is the oil filter looking device attached to the air box for?
  7. kerf

    kerf Guest

    Air filter, the original one that came with the engine.
  8. Alaskavan

    Alaskavan Guest

    Nice work Kerf. That would probly be a good reliable commuter.
  9. loquin

    loquin Active Member

    Very nice, Kerf...
  10. ibdennyak

    ibdennyak Guest

    Nah, we won't boot you for building a .......moped. :grin5: Some of us have one too. Sides, it's automatic....still fits the description.

    Couple questions......I'm curious about your muffler. Always interested in the quest for quiet. Also, where did you get your CVT. I have an idea kicking around for a full suspension stretch, and looking for an alternative to a Nu Vinci. I used to have a scooter site that carried them, but they don't anymore.

    Nice job by the way......I like it.
  11. kerf

    kerf Guest

    The only dealer, that I could find, that had CVT's in stock was Fancy Scooter. Others still list them but are showing out of stock but that was several months ago. The straight through glass pack is a simple design, used on many motorcycles. It was louder than I wanted, so I made a spiral baffle from 1/8" thick flat aluminum. It will create a little back pressure, because it is inside the core tube but it doesn't create any change in direction for the exhaust gas. It did lean out the engine somewhat but a couple of carb adjustments took care of that.

    The scooter muffler I bought, has a 3" outside diameter so 3" exhaust pipe can be used to extend the housing. A piece of 3/4" tubing, fit tightly inside the muffler exhaust pipe, so after drilling about 150 holes in it and welding on a 3" end plate, I had a core tube.

    I created a little stir in the community yesterday evening by riding the bike up the very steep hill in front of my house. A hill I never got up before. Several neighbors wanted to know where they could get one, hummmm!!!
  12. loquin

    loquin Active Member

  13. loquin

    loquin Active Member

  14. Richard H.

    Richard H. Member

    There is some fine print below, on that link:

  15. kerf

    kerf Guest

    My 11 tooth sprocket is installed on the CVT and I've run it with both the 72 tooth and the 63 tooth. I have also confirmed my calculations on the high speed ratio of the CVT at 2.875:1. The 72 tooth gives me the gearing of my old Staton single speed box but I think I like the 63 tooth. The higher ratio will actually slow the bike on top end because over gearing won't allow the engine to gain full RPM but it will cruse at 35 MPH. I still have more riding to do before I make a final decision but I'm getting closer. My pedals have cob webs on them, maybe I should keep the engine off for a while because my pants are getting tight around the middle.
  16. kerf

    kerf Guest

    Took a good hilly ride this morning and have decided to go with the 11/72 - 18.82:1 final drive ratio. Gotta let my beast breathe, a little higher cruise RPM but I want the added performance.
  17. loquin

    loquin Active Member

    I think that's a good call, kerf. Everything I've seen says that you need to gear the system to allow the motor to hit full RPM, else you end up always running in 'reduction' mode in the CVT, which is harder on the belt.
  18. kerf

    kerf Guest

    Just got back from a test ride. Mm, mm, mm. how sweet it is!!!!!!!

    On the negative side, 7:00 AM I took my new RC plane to the open field outside the baseball diamond. Things were look'n good, when I looked to see where I walk'n and flew the $#*& thing into the scoreboard. Hit hard enough to rip both wings off. Glad I ordered more wings and horizontal stabs on Friday.

    Win some, lose some.
  19. kerf

    kerf Guest

    Well, it looks like kerf is finished, maybe for good. The outside plate on the variator has cracked where the shaft goes through. It doesn't appear to have the beef to handle the load. I MIG welded the crack but but another appeared on the other side. Unless someone has an idea, I may be through with the whole MB concept altogether.
  20. kerf

    kerf Guest

    My CVT Parts

    See if this helps.

    Attached Files: