Modern Vespa

Hello Everyone
I wanted to replace the rollers and belt as the acceleration of my 125gt is not as great as I thought. I have changed everything but there is still something wrong.
With the bike on the stand when I try to accelerate the I need to twist the manopole half way to get the wheel spinning. Is there something wrong?
Also, can you tell me what is the purpose of this little cog?
Thanks

That little cog is the starter Bendix.

You need to sort out whether it is not accelerating because the engine revs and the CVT doesn't run, or whether it doesn't rev at all under load without excessive throttle.

I went for a spin and seemed to be more responsive. Usually when scooters are on even without accelerating the wheel should spin. I can see that the wheel is trying but it is very slow.
Any idea mr72?

It could be there is a problem with the centrifugal clutch.
Weared friction shoes, maybe. Then the clutch needs a higher rev to engage.
Once engaged it should feel normal.

What is the mileage on your GT125?

16k km but the maintenance from the previous owner was very poor.
I have attached a pic of the clutch.

Have you tried to rotate by hand the rear wheel?

Does it spin with little friction or you need to put a lot of energy in it?

When engine is cold and on the centre stand, does the rear wheel try to rotate, without you accelerating?

You could take the belt off again and see if there is some binding on the rear wheel by hand...

I can rotate the wheel by hand and it doesn't look it is not hard.
When I leave it on without accelerating I can see the 19mm nut slightly spinning but the wheel stays still.
Basically you think the wheel axle is kind of stuck? Or is it something to do with the brakes?

If you can easily rotate the rear wheel, no, nothing wrong with the brake or the bearings...

The only thing left is to check the air filter, spark plug and make sure the clutch bell is not glazed...

Other than that you may want to check the front wheel as well for binding...