Vari Tuning

[90GTVert]

This information was provided by 2strokd.

Heres a good way to manipulate the way your vari works to give a better launch, or more top-end. Its up to your needs.
You start with a set of washers, or shims of the same diameter of your drive boss. Mine were a bit big on the OD so i had to shave em down.


Sometimes these can be bought from scooter parts suppliers that will be a direct fit to your crank and drive boss. I couldnt find the exact size i needed so i improvised
Assuming you already have the CVT cover off,
remove the outside half of the vari to expose the crankshaft and the variator drive boss. You can see here that i have no washers on the crank at this point.

Then IF you want a better take off, or launch you can take a(or some) washers and slide them on the crank outside the driveboss.
Like this.

This will limit the top speed of your scooter though because the vari can no longer close all the way. Its a give and take thing folks .
You can also remove the vari and put washers on the inside of it(between the vari and the case) to increase top speed by moving the whole set-up. I am not running electric start so my pick may look different than other Minarelli's.

Whatever you decide to do with the shims, make sure once your done the vari will tighten all the way. I have had to add shims on the outside of the vari between the 'star' lock washer and the kickstart washer to get it all tight with some set-ups.
Also its a good idea to mark your vari with a sharpie to see how for the belt travels.

[90GTVert]

Some of us have had luck finding shimming washers at McMaster.com. For the larger spline Minarelli, you can use the 16mm ID that are available in different thicknesses. The OD is a little big, but like 2strokd said, you can file or grind them down to the proper size to match up to the OD of your drive boss.

www.mcmaster.com/#shims-and-shim-stock/=6y0nlh

[niz76]

I did some modding to my stock Variator and the results were actually quite good!
  As you can see from the mess I've made I have been digging into my CVT trying to figure out what makes it tick and what I can do to get the most out of it.

Being pretty new to the 49cc scoot world, I started doing mods kinda willy nilly and after getting a little over zealous on shortening my drive boss and making my scoot practically un-ridable, I have clamped down on my scientific method and have a true appreciation for a 1mm change in my scoot now!

  I will try to emulate Brent's attention to detail and excellent display by laying out exactly what I did on my variator mod, and what the results were...



After studying my CVT I have been desperate to get the belt to travel further up the Variator, as you can see by the groove worn into it in this pic I have been stuck at this same crappy max belt travel for a while now. 8.14mm of variator left after doing the "marker test". 


After digging through the tech section I should not have been surprised to see that Brent has already broached this subject-and laid it out beautifully. I really wanted to give his home brewed over-range variator a shot, but after realizing that the stock Variator has these straight sidewalls that simply bring the roller weights to a dead stop with no real chance of pushing the movable face out further, (He used an aftermarket Hoca clone variator) this mod was almost dead in the water before I even got started as I have only my stock variator and spent my monthly scooter budget already. lol.

 
The aftermarket variator Brent used has ramps that can take the roller weight right up steep ramps to the point it opens the variator up so much, that the plastic guides actually go past their posts and cause damage. The out-of-the box over-range variator- and the home brewed one Brent made alleviate this problem by having extended posts (and an actual larger diameter drive face) to let the variator really close up and (or open up-whichever way you look at it) squeeze the belt outward for some serious top speed! Unfortunately I don't have the $400 for that sexy beast . 
  So what to do with this stock variator? 
Well the scooter tuning bug has really got me so there was no way I was just gonna put the variator back together and live with it  
I originally just planned to thin the sidewall where the roller weights hit to give them a bit more travel -resulting in the variator faces sqeezing closer together) but after attacking it with my cheapie Harbor Freight rotary tool (and tons of grinding bit changes to find the best one) I actually ended up with more of a "ramp" for the roller weights similar to that Hoca clone variator in Brent's experiment. I tried my best to make them all match. I think the specs would fly at any Chinese factory Haha. 

The roller wights can roll right up the edge now and it seems like this about the max I'm gonna be able to get it to open as any further and the torque would seemingly be supported by only the plastic guides-with no metal behind them to support the load- and would probably rip them to shreds. I should probably also note that I have already previously modded my variator drive faces by filing them as I learned from Brent's article. Thanks!

My drive boss (with spacers) is also limiting how far the variator can close. On a side note- when I went willy nilly and shortened my drive boss by 3+mm a while back (whoa! not even drivable taking off in that "gear" lol) I corrected the issue with one of the only things I had on hand at the time I could get to work; copper pipe. 16.25mm O.D. (5/8"). I have had these in use for 200+ miles now and they are working out flawlessly. I have been experimenting with drive boss length by sanding these down a few tenths of a mm at a time (I learned my lesson in making too big a change too fast!) to keep my belt in "low gearing" for best take off with the best top speed I can manage (variator closing more). Like everyone says it's been give and take...

I put the copper spacers in before the drive boss as their O.D. is not large enough to grip the belt if I had them on after the drive boss. They don't interfere with anything going in this way.

Back to this variator mod. I gave the drive faces a scuffing with some 220 grit sandpaper to promote belt grip and hopefully coax the belt a little further up the variator face! Hoping the roller weights will expand further now and get me past that danged groove. Here you can see after the scuffing, the groove is very prominent.

Now it's time to put it back together and try it out! In my haste to rip this baby down the road I almost re-assembled the CVT without any roller weights lol. My before mod speed is 40 mph. at an unnervingly high 9400 RPM. I have 6g roller weights in although I prefer 5 or 5.5 as I am a heavy rider at 260 lbs. but I am trying to lower my WOT throttle cruising RPM as 9400 just seems and feels too high. Of course, I like the lighter roller weights because they give me a faster launch but ya know- "It's a give and take thing..." I have not changed my drive boss length for this test... Speeds readings are from 'Ulysses GPS speedometer' on my phone, not from the speedo.

The results are in and they are good! I gained 3mph top speed woohoo! 43mph now.  The mod has also lowered my WOT cruise to a better-feeling 8900RPM. I like the direction this mod is taking... And my marker test results... drum roll please... 5.06mm! Past the groove yay! 

I am hoping that thinning the side wall of the variator to give the roller weights a bit more travel hasn't negatively affected the structural integrity of the variator. I'm not thinking the roller weights have enough mass to cause a problem but at 9k+ Rpms who knows... maybe something to think about before grinding away at your only variator like I did lol.
  So that's it. That's my mod. I raised my top speed by 3mph and lowered the RPMs by 500. Take off launch is still the same. Total cost: 0$ I seemed to have given the ol' "give and take" a kick in the nuts on this one! Maybe I will press my luck by shaving a bit more off my drive boss spacers and going back down to 5g roller weights  
 Hope this inspires somebody as so many others mods have inspired me!
Cheers!


Thought I'd share a pic of the fruits of labor

[niz76]

Here's how I 'turned down' the OD of the drive boss spacers.

I found a cut-off wheel chuck meant for a drill- perfect to chuck the washers into!


I centered the washers as best I could and chucked the getup into my electric drill. I simply spun the washers in opposing direction to my grinder wheel and voila! A redneck lathe!


I sanded the edges across a peice of sandpaper on my workbench to de-burr them. Here's a couple pics of the spacers stacked on top of the drive boss:


In the second pic you can see that I did 3 at a time- they look like one thick spacer!
Like I said- I know this isn't terribly interesting but hey maybe someone is wondering how the can turn down the OD of their spacers accurately without a lathe. This worked great!