[xlint89]

The only thing I would like to add is the clutch on the driven pulley wasn't mentioned.

You see the piece with the 6 holes in the video? That's the clutch "bell". Inside of it is a centrifugal clutch that can be tuned by using different strength springs.

So, as the engine sits idle, the clutch is NOT engaged and the kart is in "neutral" if you will. Once the engine RPM raises and engages the clutch, it expands it's arms (just like brake shoes on a car) and the clutch bell will start to spin.

As the clutch bell spins, it turns your internal gears, which turns your drive sprocket, turning the drive chain, and finally your axle sprocket which turns your tires.

Different strength clutch springs will affect how hard the clutch engages. If you install 2000 RPM (red) clutch springs, the kart will launch really hard as it requires higher engine RPM to engage the clutch. Stock clutch springs will be "weaker" and allow the kart to take off at a lower RPM and engaging sooner, thus making a smooth start.

So as you can see there are MANY variables that can be altered in order to fit your personal preference.

Variator rollers/sliders

Contra clutch spring (big spring)

clutch springs

internal gears

Drive sprocket (not very common to be changed, but COULD be)

Axle sprocket

All of these can be adjusted, but the easiest and most common mods are the variator weights/sliders, (10g -12g is normal as noted above) and the Contra clutch spring (big spring) usually using the 1500 RPM (yellow) or the 2000 RPM (red)