Dialing in the CVT (slider weight)

[jeffwah]

Background: 50cc TaoTao 139QMB skeleton scooter (a far from street-legal frame & engine on wheels).  New 1000 rpm torque spring, performance CVT, performance air filter, performance CDI, adjustable carb (20mm I think), 95/38 (main/idle), new 12V 6AH battery, new belt Gate Powerlink.  I weigh about 170.

Just recently adjusted valves (.005/.005).  Louder tick than preferred, but was hoping to resolve a hard starting issue (it didn't, but that's a different topic and really just an annoyance, priming the throttle a few times before startup helps a lot).

I have been experimenting with all of these different rollers and sliders to dial in (tune) my CVT set up for optimum acceleration and top speed.
4g Variator Rollers (orange)
5g Variator Rollers (red)
6g Variator Rollers (white)
7g Variator Rollers (black)
5g Variator Sliders (orange)
6g Variator Sliders (white, current): 9/20/2015
Hint to others:  buy a roller kit vs. spending a fortune like I did on all of these.

Currently, with my 6g sliders, on acceleration, the rpms quickly rise but then gradually start to come down as the sliders/CVT do their job.  On hard acceleration, the situation is a bit worse... rpms really scream and then after a few seconds start to come down as the scooter picks up speed.  The sound of the engine makes it seem like you would be crazy fast off the line... but it's not (yawn as I pick up speed).  I read several articles where many people are saying, if tuning by sound (or tach), you want your rpms to sound/stay consistent throughout your acceleration to WOT.  In my case, the acceleration seems sluggish on an aggressive or mildly aggressive take off.  Does this mean my sliders are too heavy because I'm shifting too quickly to a higher gear?

I'm thinking of mixing 5g & 6g sliders (to achieve 5.5g) to see what happens.  BTW - with 5g rollers, performance feels about the best I can get so far.  With 5g sliders, rpms are too high for my liking, so I thought 6g sliders "should" be perfect, but it's not. Any opinions on my situation... or am I looking at and obsessing over the wrong thing.

On a skeleton bike, you have to go by sound or feel a lot... because there are no gauges.

[90GTVert]

If the RPM is peaking when you launch, you may need to look to the clutch springs. Usually RPM will shoot up till the clutch is fully engaged shortly after takeoff on a throttle-heavy launch. Ideally you want to keep the RPM in the peak power at all times under WOT operation, but what is ideal and what really happens are usually different. If your primary issue is with launch, try softer clutch springs. You may be revving beyond peak power. There's also a chance that they're not engaging until after the CVT has already began shifting ratios, so you don't really get that "1st gear" take off, but instead experience something similar to taking off in 2nd gear.

Once the clutch engages, from there and faster is where you should be looking to the rollers or sliders to change RPM. Check out a few of the topics in the FAQ under CVT tuning and performance and I think they will be of help to you.

www.49ccscoot.com/faq/faq.html

[jeffwah]

Here is an update. I left my new 1000 rpm clutch springs in (which seem slightly stiffer than stock either because they are new and/or because stock is 800-900 rpm similar to the stock torque). Not wanting to take my clutch apart yet again, I switched to lighter sliders (decreasing weight from 6g to 5g). Now, my throttle-heavy launch is tolerable (better than stock), but the real improvement is my RPMs seem to now stay close to peak power at all times under WOT from 0 to max mph. The engine no longer seems to surge during initial acceleration. So I think ultimately with my original setup, I was simply shifting too early.

I would have never guessed stiffer clutch springs might require lighter weights, while a stiffer torque spring might require heavier weights. Dialing in the CVT and clutch sure is a pain (time consuming trial and error).