CVT CVT For Smaller 4 Stroke?

[loquin]

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

 

[ibdennyak]

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.

 

[loquin]

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, ...

 

[ibdennyak]

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. 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.

 

[Deleted Member 4613]

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.

 

[mlcorson]

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

 

[TREEWK]

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.

 

[Deleted Member 4613]

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

 

[TREEWK]

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

 

[TREEWK]

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