CVT Completed Frame Mount CVT

[heathyoung]

The freewheel is a standard ISO thread, just get a better one that is designed for some serious abuse - SBP sell a serious unit that will fit your hub just fine...

http://sickbikeparts.com/catalog/product_info.php?cPath=21&products_id=62

Its a 5 hole mount, so you would have to redrill your sprocket, but it would be pretty indestructable...

I wish we could get those CVT's locally in Aus... Dern it...

 

[capturedbyrobots]

I took some pointers from the folks over on GopedNation.com and rebuilt the CVT with new bearings and modified the housing as shown in the pics for better cooling.

I just used some relatively cheap bearings from McMaster-Carr, but it seemed to make a good difference. The bearings I used were all rated for 1500lb axial load, and they were very smooth rolling. I also ditched the grease in the gearbox in favor of 10W30 motor oil. There is a lot less drag in the gearbox now, but the oil leaks slightly where the driven shaft goes through the inside of the CVT box.

I took the bike out today and clocked it at 35 mph, and it still has enough torque to do burnouts. The only weak point I'm currently having is the freewheel that the rear sprocket mounts to. I've smoked two of them now from abuse. I just need to stop abusing it or find something stronger.

LOL, I like the swiss cheese belt cover.
Venting can only help.
I was one of the main guys at GPN doing a lot of the mods on the CVTs.
I love these things. For hills, there is no comparison (except a much bigger motor)
As well, it allows you to run serious gearing and still pull it,
without overrevving the motor.
I prefer to max out about 9k rpms, as that's usually where most power is produced with my 2 strokes
so the motor isn't screaming 12-13k or higher.

My goal would be to have an upgrade kit for these china CVTs which would have
1. New variator shaft (with closer tolerances and hardened)
2. A beefier cap on the driven shaft (those little nubs can keyhole the thin sheet metal cap quickly, messing up the shifting.
3. A freewheel mounted at the sprocket output.

Did you play with the belt tension (re. shim?)
It can make or break the tuning of that CVT.

My big problem with the vari shaft was that it did not fit well in the
clutch bearing's inner race. It spun freely inside them.
Thus it would wobble slightly, and shifting smoothly suffered.
I JBwelded it into the races once, and they it ran so good until the JB weld busted out.
Maybe Threebond 1211 will do the trick, or a hammer and some
thin copper shim material. If there was only a third bearing at the end of the variator shaft, so many problems would be avoided.

 

[Shrapnel]

I tried tuning the CVT before I rebuilt it and just made it work worse. I first tried removing 3 of the variator weights, then shimmed the rear spring, but was never as satisfied with the results as when I just ran it stock. So for right now, I run it stock.

I've ordered some variator weights so that I'll be able to make small incremental changes to it. I don't really plan on shimming the rear spring at all. That just made it stay in torque mode all of the time and killed my top end.

My engine is stock as well (Zenoah 51cc).

 

[capturedbyrobots]

Fair enough.
Being that the motor is stock with no tuned pipe,
sounds like you're ok.

When you get the weights, I'm sure finding a mid way point
between 30g and 15g will have you performing better.

 

[Nuttsy]

Yeah, I tried removing 3 weights with similar (poor) results. Will be waiting to hear if slightly different weights will kick it up a little.
About the only thing so far that made a HUGE difference was changing bearings and I went overboard and filled the gearbox with 80W90 gear oil that I had on hand. I did the both at the same time so I don't know which one is the clear winner but that CVT does NOT whine anymore! Now its just motor sound again like when the Robin was a friction drive. I may try poking a FEW holes in the case. Shrapnel, have you noticed any belt 'dust' coming out since venting the cover? I won't like it if it gets messy
WC

 

[Shrapnel]

I haven't had any problems with belt dust yet. I left the top and bottom of the cover solid, and only drilled holes on the side and back. Most of the belt dust still collects inside the cover. My cvt used to get really hot, but after the swiss chesse effect the cooling seems to be stable.

I don't know if I really created any more cooling flow, but I have enough holes that no heat is ever going to be trapped inside. I'd run it open if I could, but that would create a safety hazard with were the engine is mounted.