Snake Eater CVT

kerf

kerf

New Member
Full Suspension With CVT

I've been working on this build for several years in my head and at last she's a reality, a full suspension bike, with a hot motor, running through a CVT. I must say, I'm very pleased with the results so far, although I've only had several shakedown runs. That will change tomorrow and big time on Sunday. If everything goes well, I believe I will crossed the line between motorized bicycle and moped. Thanks goes out to Neat Times for his inspiration and consultation on this project.

http://motorbicycling.com/f36/cvt-rack-mount-7265.html

One day a little over four years ago, I found myself staring at a weed whacker engine and a bicycle and pondering, could this work. To make a long story short, I bought a Staton friction drive kit with a Tecumseh TC300 and made my first build. About a week later, I built one for my wife and we began riding together. Always looking for more speed and power, I swapped the TC300 (junk) for a Mitsubishi TLE43 and found what a quality engine was all about. Rough roads were wearing a little thin, so again I upgraded to the Mongoose full suspension and later to a Staton Chain drive. The little lady went through both TC300's so I bought the Chung Yang R460 for me and gave her the TLE43. I created a two speed on the Staton box and it worked well but that CVT bug was always in the back of my mind.

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.

The bike is quite, accelerates like a car, eats hills and hits 35 mph at 6800 rpm. Don't know about top end yet but the R460 will wind out above 11,000 rpm. I hope I'm back after my hard runs with good news. I've included pictures of the bike, before and after the build.
 

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Well, I've put about 30 miles on the bike and a few issues came forward. When I left Saturday morning at 5 AM, the bike was acting like it was running rich but by the time I got home there was major power loss. The spiral baffle had deformed with heat and restricted the exhaust. Out at 5 AM this morning, sans baffle (need something else, chain saw with wheels) and the performance was back and the ride was really great. The CVT takes some getting used to because when you hit a hill, the bike slows down but engine RPM remains constant as does engine loading. I think I can gear lower because at 35 MPH, she is still below 7K, max torque isn't reached until 8K.

My 14 tooth and 72 tooth, combine for a 5.14:1 ratio. I think I can find an 11 tooth for the trans and I already have a 63 tooth which would be 5.72:1 and the 11/72 would be 6.54:1. Maybe there's something there that would work even better, don't know. What I do know is, 30 miles without ever turning a pedal, in all kinds of big hills, is darn sweet.
 
Thanks Dave.

Kerf been do'n some cipher'n. The 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)

If I pick up an 11 tooth trans sprocket, this will be 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.

I'll order the 11 tooth tomorrow.
 
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KERF

Glad to hear your cruising along so well. Thanks for the heads up email!!

I have not rode my cvt since Aug 2009 when i took it to Wisconsin. Plan on riding both my cvt builds now that it has cooled off. Wanting to road test my diy axle mount build also. Once you have a cvt and a shifter bike, single speed may be lacking a bit of the fun. Time will tell.

I need to check what sprockets i have on my cvt`s. I know i could pull a two bottom plow!!! lol. My slotted rear struts won`t keep the chain tight, I have un-slotted replacements to install. All the torque from my gearing is no doubt part of the loose chain problem. Also have a pile of spring loaded tensioner parts to install on all my builds.

Nice pics.

wayne c has a lot of miles on his cvt with the hf 52cc water pump motor. I think he is still running the original cvt with a new belt, but the old belt was still good.

I think the cvt would be great on trikes and my 4 wheel joy rider (like 2 doors trike), I just need to "Git Er Done" as Larry would say.

Thanks for sharing, and the nice words for me.

Ron PS - Feel free to use my cvt avatar built by our friend "hiker Steve". .cvlt1
 

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I like frame mounted engines, but your cool build has opened my mind to full suspension bikes with rack mounted motors. I might just have to build such a dirt bike.
 
bowljoman said:
Nice build.

btw: Fancy scooter parts sells a 410 sprocket that fits the CVT and goes very well with BMX chain.
Click to expand...

I pondered the 410 sprocket and may try it one day. The only issue was finding a suitable 410 for the wheel, that would accept the freewheel and have the requisite number of teeth for my ratio. I could probably get Martin Sprocket to build one but that's lots of $$$$$$$.
 
Kerf

Nice Job Of It. I Never Got Around To Making My Brackets Look Cleaner, Like Yours. I Went On To My Diy Shifter Build. I Did Put A Hs Titan 4 Stroke On One Of My Cvt Bikes. I Would Post A Pic With Your Permission.

Did You Read My Thread To Around Post 38 And On? Thats Where I Figured Out How To Have Double Freewheels On The Right Side For $4. Plus Sh. Using The Regular Rear Wheel.

Kerf, Thanks For The Kind Words.
Ron .cvlt1
 
NEAT TIMES said:
Kerf

Nice Job Of It. I Never Got Around To Making My Brackets Look Cleaner, Like Yours. I Went On To My Diy Shifter Build. I Did Put A Hs Titan 4 Stroke On One Of My Cvt Bikes. I Would Post A Pic With Your Permission.

Did You Read My Thread To Around Post 38 And On? Thats Where I Figured Out How To Have Double Freewheels On The Right Side For $4. Plus Sh. Using The Regular Rear Wheel.

Kerf, Thanks For The Kind Words.
Ron .cvlt1
Click to expand...

Sure, you're welcome to post anything you wish. I always enjoy looking at your work.
 
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.
 
try lighter roller weights and you'll allow higher rpm at the same gearing by raising the shift to a more effective point.
 
Don't know that I want to retard the shift point very much but I wish I could adjust the shift limit. The variator will overdrive, I built a small spacer that limited the total amount of variation but where it contacted the inner plate, it would cut into the bushing area. Decided the handle the issue with final gearing instead.

While the 16.47:1 ratio would be too high for a single speed, it only limits my top end. As far as normal riding (25 - 35 mph), it works great. You can't rev the engine into the upper RPM range but you can't lug it either. Under load the CVT just down shifts and the bike may slow but engine loading remains constant. The 18.82:1 makes it a different animal, that will actually run faster but results in a higher cruise RPM.
 
It's all a matter of MATCHING variator weights, to gearing, to contra spring tension. And there's
the rub (sorry Willie S.). You can't fool with the variator weights too much on these things (.5-1gram either side of what's in it now) since you can't match them to the contra spring. There are NO spring substitutes available for this beastie.
Kerf, go with the gut and do your adjustments to the gearing. The CVT comes factory with 5 gram weights. 4g will work OK, 6 will lug the CVT. Or, a mix of the two;3-4g and 3-5g. But that's all folks! I have tried everything for springs from the hardware
store; sprinkler pop-up springs; garden hose 'kink' extensions and all manor in between including scooter CVT contra springs. Nothing fits, works or does anything to improve or work with the factory supplied match that I have found. But feel free to try--think outside the box and get creative.
My best advice at this time regarding "gearing/performance" is stick with the factory setup and adjust elsewhere to keep the rpm in the power band. Don't lug the CVT because the belt will slip and add too much tension/torque to the main variator shaft--not a good scenario as this will wear the shaft where the bearings live. Then the shaft will develop a wobble and the fat lady starts warming up.
Good luck and WELCOME to the wonderful world of the CVT! I love mine and wouldn't build another bike without a CVT of some sort.
 
That is TOO FRIGGIN' COOL! But the crankset on the LEFT side? man...that threw my brain into coniption mode- something did not look right!

What a great idea- gives new meaning to "Reverse Engineering!"

Doc
 
I have a question. I bought two of these CVT's from scooterparts4less. And while checking them over I found that the clutch drun was crooked,took it apart and it seems the threaded part on the shaft was made crooked. I e-mailed then and they don't have any clue. Does anyone know were to get a new shaft? Has anyone run into this?

I plan to put it in the laeth and heat to try and strighten them if I can't get new...Curt
 
Curtisfox,
It is quite common for these things to have poor quality parts.Many times the clutch drum or its shaft. The bearings aren't worth a poop either and quality replacements should be on the to do list straight off.
I had one that the threaded end snapped off while 10 miles from home (same shaft; variator end). There
are no parts available for these things other than weights and belts. And sometimes not even the belt. One solution is to get a whole 'nother CVT and use one for parts. Another solution is to take the shaft to a machine shop and have them dup it = $$$$ ! OR possibly take the shaft to a machine shop and have them remove the threaded end; drill and tap it for a bolt and use a bolt-on clutch drum.
That's it. I'm out of ideas.
Oish! I could write a book on these things. But I still like 'em.
 
Thank you. I will replace the bearings before I put them together And maybe drill and tap like you said that sounds like a good plan
 
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