CVT CVT For Smaller 4 Stroke?

Discussion in 'Transmission / Drivetrain' started by Mike St, Nov 30, 2009.

  1. Mike St

    Mike St Member

    I see where the X2 CVT has been successfully mated to a 2 stroke engine. I'm a newbie on CVTs, and want to know if anyone has adapted the CVT to a smaller 4 stroke, like a Honda GX 35 or Subaru 25? I want to develop a power system to meet Illinois law if possible. Mike
     

  2. Happy Valley

    Happy Valley Active Member

    EHO35a.jpg

    Yes to the Honda GX35 and Robin EHO35, both have the 76mm clutch and CVTs are readily available in that configuration.

    Not so to my knowledge however with the smaller engines, the Robin EHO25 and Honda GX25 both have the 54mm clutch.
     
  3. Mike St

    Mike St Member

    I am sure Staton has an adaptor to go from 54mm to 76mm clutches for smaller engines. True? This would mean I could go smaller to GX25. Right?
     
  4. Happy Valley

    Happy Valley Active Member

    I'm not aware of any adaptor that fits that description, Staton or otherwise.
    Got a link?
     
  5. Mike St

    Mike St Member

  6. loquin

    loquin Active Member

    You would also need a 54mm clutch drum on the CVT, to mate with the 54mm clutch on the small engine. The adapter just allows the 78mm equipment to physically bolt up to the 54mm mounting.

    You may not have enough power with a 25cc motor, as the CVT loses some power (more than a chain drive.) For sure, you can't plan on high speed with it.
     
  7. Mike St

    Mike St Member

    The law here limits a motorized bicycle to one hp and no more than 20mph, so I'm not looking for high speed. Just moderate speed. A 25 cc engiine sounds perfect.
     
  8. loquin

    loquin Active Member

    Cool. Configure the total gearing (when the CVT is completely engaged at max RPM) for 20 MPH, then the low end falls into place. You're probably looking at a max-torque speed of 5 MPH or so.
     
  9. Mike St

    Mike St Member

    The question is with this setup, would I have sufficient power to take off from a standstill without pedaling? Any guess?
     
  10. Happy Valley

    Happy Valley Active Member

    My guess would be no but that's pretty much the case with all MBs. The nature of things with a motorized bicycle is a few pedal strokes are necessary to gain momentum to allow the small engines to assist without undue lugging.

    There is a member here, though I haven't seen him around much lately, who was happy with an EHO25 but with a GEBE belt drive set-up. He spoke of it being good for his situation: a beach town in southern CA with houses close together so he wanted it quiet, flat terrain near the beach so he had sufficient power.
     
  11. loquin

    loquin Active Member

    With a CVT ... possibly, even with a 25cc motor, so long as you've got the total gearing not too 'tall'.
     
  12. ibdennyak

    ibdennyak Guest

    Probably not from a dead stop, but pretty close. I ran a GX 25 on a minitiller gearbox (some losses) into a 18 tooth sprocket to a 6 speed 20 inch wheel. Top speed was 22 mph. My technique was to put my foot on the top pedal and swing over the saddle. Probably moving ~3-4 mph. Then just throttle up and go through the gears. Clutch was fully engaged at ~ 6-7 mph. Not a speed demon, but quiet and dependable. Love the little Honda. Eventually the gearbox wore out. Still want to build a scrubber for my old 12 speed road bike with the little engine.
     
  13. loquin

    loquin Active Member

    The nice thing about the CVT though, is that it has an extra 2.25 (or thereabouts) additional speed reduction when you engage the clutch, then, as the RPM goes through the engagement points, the ratio shifts to 1:1. Gear the rest of the bike for a top end at about 20 MPH (for a 26 inch bike, you're looking at 30:1), the effective gear ratio when you're taking off is 67.5:1... So, even though you lose apx. 15% of the power in the CVT, ...
     
  14. ibdennyak

    ibdennyak Guest

    Right Lou. That is kind of what I was saying. On my set up, wound tight in low was maybe 8-9 mph. I probably could take off without pedalling, but it was much easier on the clutch to just get it moving. Had to get on it anyway.:grin5: I'm not familiar with CVT losses, but tossed in the gearbox losses for comparison. The CVT might even gear lower than my low, so it could be as good or even better than my rig was. I do have a little Honda 50cc scooter with a CVT....very smooth. Acceleration is surprising....for 50cc.:grin5:
     
  15. Mike St

    Mike St Member

    I conclude this is a very promising concept, that justifies time and money to develop. The slight reduction in hp with a cvt is actually better to meet the hp requirement of the law here in Illinois. I'm excited to work on this.
     
  16. mlcorson

    mlcorson Member

    Mike:
    Check out this thread below. I'm not sure I understand the whole CVT thing, but I like the Bimoto concept of using a smaller engine to drive through the bike's own gears. I also would like a rear, behind the seat setup.
    http://www.motoredbikes.com/showthread.php?t=24006
     
  17. TREEWK

    TREEWK Member

    Mike, Nuttsy Has Been Running A 35cc Subaru 4 Stroke On His Cvt Cruiser All Summer. 78mm Clutch. Peaks A Little Ovr 25 Mph. Check Out His Threads (cvt On Restored Cruiser) He Has Other Threads With Inprovements. I Have Posts Of Mine In (cvt`s And Comet Drives) Mine Start Around Post # 57.
     
  18. Mike St

    Mike St Member

    I have a couple of concerns about CVTs after looking a all the posts: The CVT reverses the sprocket so a jackshaft has to be used or the motor has to be amounted all the way to the side, rackmount style. To mount it over the back wheel directly is very complicated. So the end result is a motor way off to the side of the rear wheel and a high center of gravity. It's not the perfect solution I thought it was. Mike
     
  19. TREEWK

    TREEWK Member

    Mike, My Builds Drive Off The Right side of The Rear Wheel With 2 Free Wheel Brgs. Has Been Trouble Free. The High Weight Has Not Been Noticeable. At My Age The Problem Is Getting A Leg Over. One Of My Cvt Builds Has The Cag Pocket Bike Motor, Much Lower (horizontail Cyclinder). Lately Have Been Riding My Titan Shifter, The Shifter Gives Control Over Motor Rpms. Ron
     

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    Last edited: Dec 14, 2009
  20. TREEWK

    TREEWK Member

    mike, built my own mounts etc. then i bought 2 rack mounts from "bicycle-engines.com". but have not used them. i think their mounts are a real bargain at $49. if you order ovr $100. they may still have free shipping. they come with a large assortment of extra adjusters etc. much better than building your own. can be used for several set ups. trying to find the mount pics. ron
     

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    Last edited: Dec 14, 2009
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