This mod will work for most variators, even the stock one. You need lighter roller weights/sliders with this mod. The drive face shave allow you to run lighter rollers or sliders while achieving top end like a heavier roller. It maintains high revs better too. You will need a gram scale and a file to lighten the insides of the rollers/sliders to achieve optimum results. Even .1gm makes a difference when tuning.
I've tried this with both the KN and Polini, ya just have to lighten up the weights.. I run 5.2s in the Polini and 5.3s in the KN. Both will get to 46-47.
I got a request for more info on this, so I thought I would post it up again..... Tests were done in 70+degree weather....

Make sure to do all testing with a new belt, I prefer the Daytona kevlar sold at Battlescooter or Bowls, or the Kitaco at MX-Performance. Gates belts while very inexpensive, don't seem to perform as well.

If you have a Polini, get the clutch springs, cuz 1-5mph sucks... I didn't like the top speed of 41 I was hitting with the KN before my rev limiter would kick in. The pay off was worth it though, with the KN, the motor revs higher thus keeping your speed up.
I shaved my drive face so the belt would push up higher. You can run 45+ depending on how much tuck you have. My jaw dropped as I saw it go past 45..... I'm now past the LED on the speedo going down hills.... 52? I weigh 220.
I only have a pipe as far as performance goes. KN variator w/5.3 & 5.1 Met Rollers, stock airbox&carb, NO CDI, shaved drive face, Leo Vince unsilenced pipe & a chanito shield.
You can shave the drive face $25, or the boss drive face $15. Both will push the belt higher up. The only draw back is 0-3mph kind of slow, then kicks in .... The take off of the KN with a stock setup rules. If you use sliders, 0-3 mph rocks! I am using Met Rollers now, and have inverted the face on the shaft to use it as a lathe, I sanded the lower portion of the face so the belt goes all the way down, now it almost hits rev limiter at take off.
Peeps think that a drive face shave is ghetto, yet I'm rockin 45mph stock. Good enough for my fat ass.


I shaved/sanded a little too much off, so I put a 9/16" machine washer before the variator, so the splines don't get shredded when tightening the final nut. I used a piece of sand paper folded in 4ths and dragged the drive face over it left to right, then up and down. [b]Shave a little at a time, then re-install and take a ride. Repeat this process until you get 1-4 mph more topend. If you shave too much, you will need to put an extra machine washer in first before the variator.
Again..... try different combos of rollers, test test test ! And get or make a variator tool if ya don't have one.
Peace!!!

weekend project here i come

you should make it a midnight project. i did the same thing while using sandpaper. i believe 200 grade.

Did you get similar results?

Shave a little at a time, when you start to see some alloy dust on the sand paper, it's time to put it on and go for a ride. Make sure not to shave off the whole lip. If you shave too much, you will need to put in a washer before the variator goes on, so you don't damage the splines when the final nut goes on. Leave the cover off so its quicker to take on and off.....
Find a good long flat road to test on..... The trick is to find the sweet spot almost before the rev limiter kicks in. If you shave too much, the belt will stay higher and the Ruck won't have enough power to get to the top of the variator. I'd say 44-45 hitting the limiter. If you feather the throttle, you can actually get a little more out of it too.
It's always a good idea to have a new belt too, the new belt will ride higher on the variator, than a a worn thinner belt.
Make sure to get yer Ninja Ruck Tuck goin...... wind is your enemy.
The wife was complaining I was going faster than her. She doesn't have a Chanito shield like I do. We changed Rucks. I tucked on her Ruck, and was cruzing by her on my Ruck. If you don't put your legs in and tuck, only plan on hitting 40-41.
Good Luck!!

my results were that the belt rode alittle higher than the non-shaved face. i did get alittle bit more speed. i used to hit 40, after the shave i would hit 44 on good days and 42-43 on regular days. but, my results could have been altered by other things also.

Thanks, I was trying to find this somewhere and well here it is,

Many Mahalo's for reposting . . .

+1 No kidding, i did this mod yesterday, and had some q's about the washer placement. I didnt put the washer on after shaving and ganked up the spline a little.
Fixed that, and put the washer behind the kick start plate, but it seems to be dragging somewhere, so i will put the washer behind everything and see if this helps. I didnt notice any improvements in speed, but that kn vari sure gets you there quicker!

If you shave too much off the face, the washer and nut can mess up the splines. I used a 9/16" machine washer from True Value Hardware. I actually shaved the washer down a bit too..... This needs to go on before the variator & drive face. Note on my diagram I have a washer on first, and last. If you do a slight shave, you don't need the first washer. You can also just shave the drive face boss, as it is cheaper to replace, but it is a pain in the ass....... Hardened steel vs alloy.
1. Put on machine washer
2. Put on variator and drive face boss
3. Place belt over shaft
4. Place drive face
5. Place Starter Ratchet
6. Place washer
7. Place nut

I did this mod because I like the acceleration of the KN, yet don't like the top end. The polini has the top end, but the acceleration bites on a stock motor. I have a Polini, but like the KN and the shaved drive face.
I'm running 5.5gm rollers and a Daytona belt. I might up it a little once it gets warmer out and the Ruck makes more power.

A video of what you did would be sweet.

What grit did you use?

Sandpaper, nothing too strong.....I used a finer grit. A vid would be a good idea.... I work on getting one up.

Just to be absolutely clear, shave a little off of the drive face lip as pictured, with sandpaper until you see some metal flakes, then slap it on and go for a spin? And if I shave too much, I need to do number 1. I'm guessing the shaving of the drive face should be very minimal.

yes.... if you shave too much and try to tighten the nut, the splines will be exposed on the shaft and you will mash them all to hell. Nothing that a small file couldn't fix. Just be careful. Take many test drives...... note acceleration to a certain distance as well as top speed.

about how many mm did you shave off the lip before you need the first washer on before the variator? I shaved the lip on the drive face and now the kick starter washer and outter washer do go on further but i didnt need another washer yet so thats why i ask. maybe i havent taken off enough material

go fo a little riding then look at the variator to see how far out the belt is riding. if it stops moving out, dont bother shaving anymore because you dont have the power to go any faster

did mine with 180p sandpaper, just shaved off a little, test fitted, shaved a little more, tested untill i was satisfied that i wasnt going to f-up my splines and rode it. between that, new rollers, spark plug, and a bigger slowjet, it got me 4-5 more mph.