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Q. What weight of rollers or sliders should I use?

If your scooter ran well and you're only replacing the weights because of flat spots or other damage/wear, then the simple solution is to use the same weight that the current rollers are. The problem that most frequently comes up is that we don't know how much the stock rollers weighed. Unfortunately not all scooters use the same weights, so it's hard to look up a particular make/model and find out what stock is with much certainty. The exception being some Japanese and European made scooters that may mention the weight in a service manual or it may be able to be found through a search. If you have a small scale, even if you find a listing for your scooter, I would suggest weighing the rollers/sliders yourself. If you don't have a small scale that can read to at least an 0.1g resolution, consider purchasing one. They can usually be found on eBay or other sites for roughly $10 and they are an excellent (nearly essential) tool for anyone doing much CVT repair or tuning. I have heard of people taking roller weights to the post office or other shipping store and asking if they can be weighed. I would suggest cleaning the rollers thoroughly if you try this.

If you are attempting to get more performance out of your scooter with a roller weight change, then you should follow a tuning process to select the weight that works best for your specific scooter. Many have posed the question on the forum, "What weight do I need?". The problem is, there is no one-size-fits-all solution. Too many variables are at play. You may get lucky with a recommendation for roller or slider weight that turns out to be perfect or at least an improvement, but following a tuning procedure will more certainly lead you to a good result if properly executed.

Before mentioning any specific procedures, let's talk about the very basics of roller or slider weight selection. Here's one of the most important things you should know :

Lighter Weights = Higher RPM
Heavier Weights = Lower RPM

Let's go over that once more to help it sink in. Decreasing roller or slider weight should increase engine RPM. Increasing roller or slider weight should decrease engine RPM.

You may find other sources stating that heavier weights will increase speed and decrease acceleration and that lighter weights will increase acceleration and decrease speed. While there is some truth to those statements, I feel that this is an improper approach to explaining roller tuning. This gives some novice tuners the impression that heavier weights will make them faster or lighter weights will make them quicker, and that is not necessarily correct.

Your goal in selecting rollers or sliders (as with most CVT tuning) is to find the setup that allows your engine to stay within it's range of peak output as much as possible at wide open throttle (WOT). Peak output is from the engine's torque peak to it's horsepower peak and just beyond it, though you will generally find the best performance staying as near peak HP as possible. If you happen to have a dyno chart from your engine handy then you would swap weights around until you were as near those spots as you could get it. Most of us do not have that luxury, but a trial and error style of tuning process works very well to find the most power even when we don't know exactly where it is.

You should have an assortment of weights on hand for tuning or be willing to modify weights to make them lighter or heavier. Multiple methods of modifying rollers or sliders to change their weight are covered HERE. You will also need to be able to remove and install the variator and CVT cover, which are shown HERE and HERE.

The process is pretty straight-forward. Select a spot to tune. Choose a place that you can ride WOT uninterrupted, safely, and legally. Preferably flat roads with little or no traffic. A track would be great if you have that option. Some industrial parks are essentially uninhabited in the evening or on weekends and have long flat stretches of road. It's your responsibility to make sure you aren't trespassing or breaking any other laws though, these are just ideas. Try to do your tuning on a day with calm winds and no unusual conditions. Heavy and variable winds can make tuning much more difficult than it needs to be.

Once you've picked out a tuning spot you'll need to make some test runs and record the results. You can do this a number of ways, depending on what exactly you're hoping to accomplish. I tend to do long WOT passes ensuring that I'm able to reach cruising speeds because I spend a lot of time cruising at WOT and record my speed and other info for each test. If your goal is to have zippy acceleration for around town riding and you don't care so much about max cruising speeds you may take a different approach such as timing WOT runs over a short distance or seeing what speed you can reach in a short distance. Whichever method you are using, you should make passes in both directions for each weight tested. This creates more data, but also aids in ensuring that wind or hills aren't skewing your results.

When doing a test run, keep an eye on your gauges... of course being sure to watch the road and remain aware of your surrounding and safe. Some aftermarket gauges may even have recall functions that allow you to make a quick pass and then see your maximum speed or RPM or other parameters while safely parked afterward. Do your pass in one direction and then note any information and observations. Examples include speed, RPM, time, and notes such as if it felt sluggish to you or as if it revved too high. Along with this, note the weights that you're currently using. Then do a pass the same way in the opposite direction on the same bit of road. Record those results in the same manner. You may find it easier to do both runs and record the results after, as long as you can remember all of the numbers accurately.

After the first run you should have notes for each direction detailing any observations and performance figures that you collected and stating the weights used. Next you would swap in heavier or lighter weights and repeat the process in the same manner. If you see an improvement then swap in a set of weights another step in that direction and repeat. For example, if your scooter was quicker or faster with heavier weights you would try an even heavier set of weights to see if improvements continue. If your scooter is slower, move in the opposite direction. For example, if you used heavier weights and performance degraded you would try lighter weights next. Keep moving in whatever direction is working until performance again declines. As you do more runs you should see a pattern emerging in your notes that makes it easy to see what works and what doesn't.

You could stop there and revert back to whatever weight showed the best results. If you move in large increments of weight, 1 gram or more at a time, I would suggest going back and fine tuning. Find the two best results and try a weight in between them. For example, if you found that 5g and 6g weights worked the best you may want to try 5.5g weights to see if you can find even better results. You can continue this process until you're down to tenths or hundredths of grams if you're motivated to do so, though most are satisfied tuning down to 0.5g or 0.25g precision and beyond there you'll spend a lot of time for marginal gains at best in most cases.

HERE is a video showing the process in action.

Even after a tuning process I like to take a ride in the same conditions I normally ride in before I consider it done. If it's a little sluggish when I'm off and on the throttle around town, maybe I'll go slightly lighter on the weights. If it revs higher than I like on the top end, maybe I'll switch to slightly heavier weights. An ideal tune would stay at the RPM we want all of the time, but since it rarely works that way in the real world there is often a bit of compromise and rider preference involved.

Here's a quick tip if you're looking to maximize belt travel for max speed with your tuning. Make a mark across the face of the variator, from center to outer edge, with a marker. Get the scooter up to it's top speed. When to take the CVT cover off the leftover mark will show you how far the belt is from the edge of the variator at speed. Measure it and make a note of that. Make another mark and try another set of weights that you are considering. This will allow you to see if your belt travel is getting better or worse. You may find that heavy weights will get you the most travel, even if they're too heavy for best performance otherwise. Again, sometimes you have to make a bit of compromise.

Marked variator.	Measurement post-test.