Modern Vespa

On a modern vespa can lighter roller weights cause the belt to slip? And as an example, are burnouts possible on a modern vespa or will the belt slip before the tire does?

Im narrowing down what can be done on a budget to my off road vespa. I've gone to lighter 7.5gram roller weights, I went to red malossi clutch springs. And I have a white contra spring with a new belt. But I still feel like i'm losing something. Sometimes the motor will rev a tad and then kinda sit there and nothing will happen, the rear tire won't spin either. If the lighter roller weights aren't the problem maybe I need to go to the red contra spring? How do I get maximum belt force to transfer that power to the rear wheel without the belt slipping?

My stock LXV150 would spin the rear wheel on loose surfaces. Or maybe it just broke traction from a standstill until it settled down. It is CVT so has a limited range of ratios.

It revs and then sits? What happens if you apply more throttle?

The rear wheel will only spin until the CVT changes to a higher gear. So it has inbuilt traction control, sort of.

I'm riding dirt. So its loose. With my weight on it the rear wheel won't spin going up some steeper dirt roads. The engine will rev a little bit and then just sit at that rev, and the rear wheel won't turn. This is at max throttle so nothing more to give. I've just gone through the carb its running smooth, it just seems like all the power is in the midrange and I can't get it down low where I need it.

Heres a little clip, you can see the tire slip and spin at one point, but then i'm giving it full gas and nothing is happening.

https://youtu.be/7S8eJaS7HK4

With 7.5 weights can we assume this is an LX 125?

Red Springs? I have never bought any so I am going to assume you have researched more than me, but don't they engage higher up in the rev range? Starting at about 5000 Rpm? Fully engaged at about 7000

Next would be the condition of the belt if it is worn and too narrow the engine will rev but the bike won't go anywhere.

This is a 2006 LX 150.

I have the white contra spring in now. I just installed red clutch springs the other day and will try those this weekend. I ordered the red contra spring but its coming from europe so it will be a few days before that arrives.

Belt is new, cleaned CVT surfaces and installed the new belt only about 10 miles ago.

i cant speak to loose surfaces...but anytime i have had issues going up hills, its because the contra spring is too weak....white is pretty soft, yellow is mid...red is stiffer...

you will want some heavier rollers if you go with the red spring....

what rpm will those red clutch springs make it engage at?..if its like plus 1000 rpm then you might be good...

Firstly instal a tachometer. Then you have some numbers to act on.

Well, at least I got the clutch springs figured out. Red spring Part # 2911326
engages between 3250 and 3750. The highest of the three colours.

I believe the gearset for the 125 is slightly lower gearing than the 150 so for off-road the 125 gearing may yield some benefit.

Keep plugging away. Eventually, you will find the optimum setting.

Correct me if I'm wrong, but that's exactly the reason why ATVs, UTVs and snowmobiles use two clutches in their CVT. One is as our regular, and another is in front pulley. It allows the engine to spin to powerful RPMs, and only then it starts to transmit torque to front pulley.

Greetings:

With engine weight + rider weight over the rear tire and only 10-20HP to work with, burnouts will be tough unless you're on loose or very slippery surfaces.

Be aware of one pitfall to stronger clutch triplet springs: It is possible to have the clutch engagement delayed enough so that the variator has begun to... um, variate before the clutch engages. You can see it on the Hondas I've owned because it is possible to observe the transmission with the engine running and the belt cover off.

What this means is that by the time the clutch engages, the belt is already 10-15% retracted toward "overdrive" and it is like starting in 2nd gear. If you go stiffer on the triplet springs, then either a lighter variator load or a stronger rear pulley spring may be needed. Both of these changes will retard the variator shifting to a higher RPM.

The stronger Contra spring is a bit more time and trouble to install, but confers the advantage of reducing belt slip. It also forces the belt more quickly into "low gear" when you let off and reapply throttle frequently, as on curvy roads or tracks.

https://scooterpartsco.com/vespa/lx-150/lx-150-drive-and-transmission/malossi-torque-driver-vespa-150-piaggio-125-150?zenid=538b56007a1c338b5fda39321b78ed78

https://scooterpartsco.com/vespa/lx-150/lx-150-drive-and-transmission/malossi-torsion-controller-for-vespa-piaggio-150-300?zenid=538b56007a1c338b5fda39321b78ed78