clutch adjustment HELP

[smith919610]

Clutch help?? I need help on clutch adjustments. I've not figured out exactly what each spring or roller do. I'm trying to get a little more power coming out of the turns. It could also use more on the gates. Everyone gains about 5ft jump on us during gate drop then when his power comes in he's able to catch back up and usually gets the holeshot or at least top 3 spots. I have an 07Apex 90 with new Koso adj clutch, 4.75 rollers, & ZTR 1500 spring. Any help would be appreciated and if someone can explain how to adjust plus what each spring/roller does and also how to know which one you need to work with I'd be grateful

[nastynotchback1]

where do yall race at?we race in ga every other week.


search this site for cvt adjustments.there is some great info floating around some post.i am going to go out on a limb here and say that your 4.75 roller are too heavy.

[smith919610]

He started the Durhamtown Series last March. Its his 1st year but he's wanting to do more. Do u know of other tracks?

[nastynotchback1]

Are you the guy that was talking about the 117cc motor forsale?my son rides the blue e-ton.

[smith919610]

Yep that's me

[nastynotchback1]

Originally posted by smith919610
Yep that's me

Okay.thats good to know.see yall next race

[tyler70t]

What belt are you running because we are running almost the same set up but with a trackside pipe and Tyler jumps out of the hole really well. We are using the 780 not the 787, longer belt may hurt you, JMO

[smith919610]

It currently has a Bando 788-17-28 belt. That's what Marc @ Hot Quads gave me. It was working great even last race he got holeshot but was sluggish exiting turns. That couldve also been carb issues. It was cold and he did have a carb issue that night. The belt that originally was on it was a Malossi 6112742. I'm not sure what goes on here. Marc has helped me a lot. We got the quad used in June. It was one of Cody Sheltons old quads. Don't get me wrong we love it. Its just we're new @ this and trying to learn. So any info is appreciated. Any1 with useful info can also call me. We just got a new Ztr 1500 spring, new plugs & boot, uni ,& Ztr chain tensioner. So maybe it'll be ready for next race. What about jetting? It has 120-40 now. What do you recommend?

[smith919610]

Another thing, my clutch is the Koso adjustable which is like japanese to me. How do I adjust it. It has 3 yellow weights that can be removed & also the springs can be moved to other holes. I left it alone & just installed it. What do I try to do, make it tighter, take weights off or what?

[bulldogfallon]

The CVT is really about math and knowing what your goal is.

Some quick pointers:

Clutch needs to engage where you start making torque (Pipe/cylinder combo decides this)

The roller weight set how fast you shift and max rpm



Clutch engagement is affected by many things:
Belt Length
Clutch Weight
Clutch Springs
Torque Spring & Roller Combo

The pulleys are like 2 sprockets that change as you increase rpm...so as an example if the sprocket(pulley) was a 17T and the rear sprocket(pulley) was a 34 then it would take 2 "Engine RPMS" to turn the clutch 1 time.

So be careful as to when your discussin stall as most link it to engine rpms, but really it is clutch rpms (not the same ratio)

So if your belt sat higher in the rear pulley then it is 1) Like having a larger rear sprocket 2) takes more engine rpms to turn the clutch once

Engaging the clutch too low can provide a drag off the line since you don't take off in the power range...If you stall too high the belt drops in the rear pulley and the cvt shifts before the wheels move....Like starting your car off in 2nd gear.

If your roller weights are too heavy it is like shifting a 10 speed bike before your pick up the proper momentum...so you always drag a little and don't get to a strong pace....

The torque spring keeps pressure on the belt and alos keeps the quaf in low gear and helps it kickdown to low gear...so a soft torque spring will make you sluggish out of corners and allow the cvt to shift before the wheels engage...the roller weight also affects how the torque spring works as well..since it is a push/pull relationship they have.

Many tune soley for belt travel, but really belt travel is a by product of a properly tuned CVT...either you get the travel or you don't....

Most put more roller weight in an attempt to get more travel, but really you shift faster which may in turn limit your ability to reach peak power

It is also important to get the travel in a usable distance...What good if belt travel at 500' when your longest run is 100'

Sprocketing is also a player in this game....


To tune the CVT a tachometer is needed and knowing what your trying to achieve....

Ex) If you engine makes peak power at 11,200RPM and with 5 gram rollers your shift too fast and rev out to 10,700...you never reach your peak power...

If you lowered to 4.75 rollers you make shift a little slower and rev out closer to the 11,200 target...


The CVT goal is for the eninge to run at one rpm (peak power) independent of what the CVT is doing.

If rollers are too heavy the engine will rev below peak power and once the pulley finish shifting the engine will take back over and speed will increase again at that point....but usually at a distance not used on the track....and provide false sense of belt travel


The tachometer is your best friend with a CVT guys....


I rambled along here...not sure if it made sense, but I'll reread later with fresh eyes and try to organize the content better.