CVT CVT Project On Restored Cruiser

Discussion in 'Transmission / Drivetrain' started by Nuttsy, Mar 2, 2009.

  1. Nuttsy

    Nuttsy Member

    Well there seems to be alot of interest suddenly on CVTs and I've been asked to show my project. So I'm gonna go ahead and post what I've been working on.
    I won't bore you with a bunch of stuff about the restore; just a couple of pics. I scored a Western Flyer cruiser for $10 last summer. The next day the guy's neighbor asked me if I wanted another? FREE. Magic words indeed. This one was a Murray West Port. Both bikes date around the '70s. So between the two, and my new best friends at, I made one really heavy bike. I guess for the purpose of this post we can refer to them/it? as a Western Flurray?
    I started with the wheels and laced 11ga. spokes from Husky onto the two rear wheels. I'm using a rear coaster brake in the front and back. I may also add calipers to it, but so far these things are working great! Each wheel weighs in at 11lbs.
    Not shown in the pics are the neat lights I'll be adding with a 12V SLA and generator/charging system. There will be a torpedo fender light up front using a small halogen reflector bulb. The regular headlight will merely be upgraded with 12V auto bulbs. There will also be a pair of driving lights next to it (Harley type setup) one a 10W halogen flood the other a 20W halogen spot. That combo was working great on my other bike and I commute in the dark and these let me see everything. Finally on the rear fender will be a Harbor Freight small LED marker light and up above on the rack a Flash Gordon looking 12V tail light, just because. The springer fork and seat give this thing quite the cushy ride.

    Attached Files:

  2. Nuttsy

    Nuttsy Member

    Rear Rack Fabrication

    I'm using the Robin engine from my friction drive coupled to a goped/pocket bike CVT. Since the CVT output sprocket spins opposite the input clutch pulley, it was necessary to mount the engine in similar fashion to the friction drive setup. That is, on the left side of the bike. The original plan was to do a frame mount, but due to the height of the Subaru engine and the offset of the CVT, there just wasn't any room in the frame without using a jackshaft. The pedals also presented the usual problem with the frame mount so, rack mount it was.
    While the engine still sits off to the left side of the rear wheel, the weight is distributed more evenly than just the friction drive setup as the CVT weighs almost as much as the engine!
    You may notice that the CVT is mounted upside down. That was to facilitate the chain alignment. If the CVT was mounted as it should be, the chain would be too far to the rear. There is an oil breather vent hole in the TOP side of the CVT. That had to be sealed to keep oil from running out as top is now bottom.
    Also, in order to be able to change the inevitable flat tire on the rear, I slotted the rear rack support (like the friction drive had) so that it acts as a chain tensioner too. The Staton kit that I had, was used for the front bike to rack mount. The Staton rear supports were too short so I had to make those. Now to change a tire is the same as any other bike and aided by the double center mount kick stand.

    Attached Files:

  3. DetonatorTuning

    DetonatorTuning Active Member

    GO , GO Nuttsy

    that IS a well planed out rack and mount. still just alittle concerned about the chain clearance going down thru the rack, maybe it's the angle ?

    are you going to match paint it ?

  4. Nuttsy

    Nuttsy Member

    Mounting the Engine

    Actually, mounting the engine was pretty straight forward. Four mounting holes on the bottom of the engine were bolted to the support frame. The support frame mounting holes were slotted to allow for engine alignment left and right. The CVT is mounted to the engine with 4 bolts inside the black cover. Also a brace was added to the mounting hole for the CVT. These holes have a rubber insulator inside the hole, although I don't notice any vibration out of the engine to worry about.
    It was about this point that I was looking at the engine/rack assembly and thinking I hated it! It just seemed to subtract greatly from the classic cruiser look that I like so much. I was this close to going to a pusher trailer or pusher side car. The side car actually will probably be my next project. I already have the 2.5HP engine I plan to use. I got it in December and have been running it a little each week to break it in. That will also use a CVT. Most likely a Comet brand. But another project for another time.
    I digress. Anyway, I decided to see this thing through to completion. After all, I could always take it off and go in another direction later. I just hate to cut that rear fender to make room for the chain. But it must be.
    I am glad though that I kept at it. I really like the CVT and the bike has more power and speed than my old one did with the friction drive. AND this bike is alot heavier.
    Also a note on the tensioner. I thought the pivoting rack would provide all the chain tension I needed. WRONG! In practice, I guess due to the long chain run, the chain was bouncing all over the place. You may be able to detect the scuff marks on the whitewalls. A trip to Tractor Supply solved that.
    Try to look beyond the raw rack and welds. It will be painted to match the bike.

    Attached Files:

  5. Nuttsy

    Nuttsy Member

    Some shots of the chain tensioner and chain alignment.

    DT, the chain tensioner kept the chain line straighter than the previous pics show. Also, I moved the front cross brace in the rack to make more room for the chain slap, which is now almost non existant.

    Attached Files:

  6. loquin

    loquin Active Member

    Very Nice. :cool2: I like it. I'll be using some of your ideas.:yes:
  7. stude13

    stude13 Active Member

    please, what size chain and sprockets?
  8. Nuttsy

    Nuttsy Member

    Chain and Sprocket info

    The chain is #41 from Northern Tools. The rear sprocket is a standard HT 44tooth I got from BGF. Yeah, I went there. LOL Truth is, it was cheap and fast. 3 days from Calif. to FL! He must have shipped 5 min after I placed the order.
    I had to get creative on the front drive sprocket. The CVT comes with a 18T (if memory serves) BUT, it is for metric 8MM chain and the shaft is splined. I hunted every scooter and gear supplier I could think of for something more substantial, yet with splined hole. No dice. Many LOOK like they'll fit but bore size is wrong. I took the CVT to a machine shop to see what they could do. Everything they suggested was twice what I paid for the CVT! I asked if I got a sprocket with the right pitch and number of teeth and with SET SCREWS, could they just bore the shaft to the right size. Well, that they could and sprockets were about $15. And another $40 to bore it out! SHEESH! Why couldn't I bore it out. So, that's what I did...sort of. Couldn't find a sprocket with the proper # of teeth that I wanted AND #41 chain, AND a close dia. bore. So I settled for a 12T 5/8" bore but for 40 chain. It took a 9/16" drill bit to open the bore to the proper size and about an hour with the grinder cutting down the teeth to fit the 41 chain. But I succeded. I'm sure there has to be something out there with a closer fit but I wanted to get the thing DONE. I also ordered a 14T with the 12 in case I wanted a little more top end but haven't machined that one yet and don't know that I'll need it. I'm happy with the performance and speed I get out of the 12. (yeah, right. temporary condition, I'm sure)
    Also, the sprockets have 2 set screws. I can turn the sprocket to the inside or outside for best chain alignment, However, the BOTH set screws DO NOT line up with the splines in the shaft. So I drilled and tapped another hole so that BOTH set screws seat in a spline groove.
    In the end then, the CVT is supposedly 7:1 ratio. I added 12T to 44T. And using one of the gear ratio calculators I 'think' I got on this site, was able to plug in the numbers and get what I thought were the right gears. Seems I did get it right. The bike will move from a dead stop without pedals (although I do pedal anyway). I guess old habits die hard, as they say. Don't get me wrong here. Its a slug off the line; but it goes. And I top out at 30. It pulls the mild hills around my house without pedaling and even picks up speed along the way. Something my friction drive couldn't do and I had to help that up these same hills or it would bog.
    All from a 35cc 4 stroke. CVTs RULE!
  9. loquin

    loquin Active Member

    Did you check here or here? They're #25 chain though...
  10. DetonatorTuning

    DetonatorTuning Active Member


    you have 6.56:1 at the output shaft in "low" and 3.15:1 in "high"

    you are going to have to add 6.5-7:1 from there to the wheel. you can go HUGE on the wheel sprocket OR add a jackshaft to your mount rack just under the output shaft.

    you don't have enough reduction yet. that's why it's a dog taking off, it may be you will also get some more topend too if the engine can rev freely up top.

    i had the same lateral slop and flop with the chain on my Staton setup, a good tensioner/ guide makes all the difference.

    Last edited: Mar 4, 2009
  11. Nuttsy

    Nuttsy Member

    I know some of you have seen this before. This is where I first saw it. However, note 2 things. It is the same CVT we're talking about 'cept with the Chrome plastic cover instead of the black one like mine. The 2nd thing is look at that ginormous sprocket on the rear wheel! It seems to go off the line alright, but with that GX35, I doubt it has much of a top end with that setup. You can't tell from the short vid and the way the guy is riding. I guess its what you're looking for. Most of my commuting is mile or more stretches with no traffic lights, stop signs etc., so I'm more interested in cruising at a decent steady speed (without going too crazy). If I were in a more city-like atmosphere, with alot of constant stop and go, I might want to have a huge sprocket on the back like that guy too. And too, I don't mind pedaling to get going or even helping on steeper hills, Its just a little harder on a one speed bike than a 21.
    I'd like to make a vid if only I knew more about it. Nuts and bolts I can do; technology, not so much. lol
  12. DetonatorTuning

    DetonatorTuning Active Member


    your points echo what i was trying to get at.

    you need to build your total overall reduction so that your engine will keep pulling all the way to redline.

    the advantage of the CVT lies in it's abiblity to "underdrive" that ratio to give you start off acceleration.

    i'd think that much like my GP460 your engine has a mid-range sweet spot just above the advertised torque peak. i gear to be running 35-40mph right there. that lets me shift down for start offs and hills and shift up for super economy cruising.

    your 4 stroke is going to give you alot of flexability due to good torque characteristics.

    i agree about the bike in the vid. i doubt it tops 25mph. and i know what you mean about doing vids, i'll have to hire my daughters boyfriend to do one for me !!

  13. Nuttsy

    Nuttsy Member

    Seems like it's you and me here pal. haha, and the guy that got swallowed by robots. AGAIN. hmmm. Mysteriously absent...
    Anyway, trust me, I ran ALOT of numbers before I dove into this project. I re-checked and it was in fact a gear ratio calculator I downloaded from THIS site. It was published by one Jim Sitton. Sorry, I've got it on my machine but can't locate the link. However, I do NOT trust this guy's speed calculations. Especially now that I have and actual working model.
    Anyway, using the calc. or even basic math, and if you believe the advertised gear ratio of 7:1 at low end, then with my 12/44 final drive, I would have a 25.6:1 on the low side. And assuming a 2:1 ratio at the high end ( I no-how believe these things can hit anywhere near 1:1 just from observing the belt at various rpms) , an equivalent 7.3:1 in full zip mode, I'm thinking those numbers work for a WIDE range of ratios. Since it seems everyone here is advocating an approximate 18-ish:1 for a single speed setup, I thought I would be in good shape. And in actual practice, seems I am. I'm really happy with the CVTs performance on the same engine over the friction drive (the only thing I can compare it to).
    NOW, that's not to say I won't be playing with different ratios in the future. I may try a 10/44;12/56; or beyond but for now; I'm good. And the BETA portion of my system is over. I put on another 10 miles the last couple of days and it seems ready. So, now I'll be taking it apart and painting stuff and replacing the fender in the rear and working on the lighting.
    All that will be killing me as I really have been into riding this beast finally. Yet I'm hoping to have it all back together for the next Tampa Bay Rally the 3rd week of March. DO-ABLE! Then I can Tweak things at will.
  14. I'm right here.....
    Personally, I do believe that a larger rear sprocket can only help things,
    though do you know what the max RPMs of you motor is?

    I was going to stay away from bike chain for this,
    because you just can't get the front sprocket small enough.
    That's why I was going to stick with #35 or 219 chain, and
    weld this style sprocket to the splined shaft 8mm sprocket, but grind off the 8mm teeth. The old sprocket would just act as a center sprocket coupler to the output shaft of the CVT.
    (ignore the bearing in the picture, I would just pop it out and weld the whole sucker on the the splined original sprocket after grinding....)
  15. spad4me

    spad4me Member

    This is what I have used in the past welded onto the ground down c-ringed stub from the cvt

    upgrade your Engine to the DAX Motor 1.5 mm
    wide 081 engine sprocket counter shaft sprocket.
    This 10 tooth engine sprocket allows you to run 415
    chains and 081 BMX Bicycle chains for lighter
    weight and more performance. Only $9.49

    I think this will work even easier, not quite sure yet though.
    TITAN Gear Box PTO and others with 6 cog
    spline. New Style one Piece milled. ONLY
    He is out of stock at this time on these. So I can't test one. YET .

    Thats dax also has up to 56 tooth rear rag mount sprockets.
  16. Okay I'm completely convinced that this is an absolute MUST DO!

    I love that setup Nutsy. I got one of those 10 tooth gears it would have bolted right up. I'm gonna be using it for when I get mine.

    I'm sure the 10 would help on the bottom end.

    How's the drag with the fixed sprocket?

    And is the 4 mounting bolts to the bell housing enough to keep things upright? Do you feel a need to support it better?
  17. Nuttsy

    Nuttsy Member

    There is definitely some drag. Ya don't want to be pedaling this thing very far although I did just to try it. You could make it home but you'll be bushed! The 4 mounting bolts would probably be enough but I went ahead and added another on the CVT. It just seems it makes the setup a little more stable when the torque is applied. Then again, it might just be in my mind but I'd rather err on the side of excess. And since the holes are already there, why not use them?
  18. Nuttsy

    Nuttsy Member

    I don't know all that much about chain drives but I don't think I'd go any smaller than the 35. These bikes can get heavy and it seems that the bigger chain might hold up better, especially with the length of run. And with a #35, what would you install for the rear sprocket and how. I guess how would depend on the bike and hub. Another reason I went with #41. Stay with the known quantity and all.
    I like the idea of using the original sprocket as a backup plate. I wonder if it could be drilled instead of welded. That would allow for quick sprocket changes if need be. I tried drilling a rear bike sprocket once and no dice. I hit it with every type drill bit I could find and couldn't even scratch the hardened surface; literally! Yet, the sprocket I'm using is hardend too and I was able to drill and tap a set screw hole. The Dax sprocket Spad linked to would be nice too if the splines were the same size as the shaft. I came across so many in my early searches that had the splines but were not of the same diameter. RATS!
  19. Nuttsy

    Nuttsy Member

    Max RPM on the Robin 35 is 7000. Max torque is at 5000. Those are no-load numbers. That having been said, with the load of a heavy bike and ME, I'll never see 7000 and wondering if I'll hit 5K. Maybe, but I have no RPMeter to tell me these things. Just have to go by the sound of the engine. Maybe one of those little tachs would be a good investment for tuning and playing with gears and such.
    Nickel and dime; nickel and dime!
  20. I am willing to bet that the 8mm sprocket can be drilled.
    Welding would be much easier though.
    The bottom sprocket could be attached best to a disc brake hub.
    Mount a brake rotor on the hub, then drill holes in the disc rotor or sprocket
    (most are aluminum so easy to drill) and bolt the sprocket on.

    Just an FYI,
    I run 25H chain on my CVT goped, and I have never broken a chain.
    25H is small but strong.
    I weigh 175, and the goped weighs about 45lbs.
    35 and 219 chain is almost the same size, and is perfect for this application.