Honda Supercub/ Postie bike clutch theoretical Question

[TrumpyDave]

Hi all,

I'm hoping someone can help me out, I'm working on a design for a competition but there's a technical question I need to figure out before I go to much further.

The semi-automatic clutch on a Honda Supercub aka a postie bike, does it engage if the motorbike is moving at speed but the engine revs are low?
For instance, if the bike is idling, then starts rolling down a hill, would the clutch engage and start engine braking? Or would you need to start revving the engine to make the centrifugal plates move into contact, where they'll then grab, spin the engine up to speed, and then you'd start getting engine braking?

Believe it or not I used to work as a postie but for the life of me I can't remember how it worked, I think I remember there being engine braking, but the engine would have always had its revs up so the centrifugal clutch would be engaged anyways... My thinking is that the centrifugal clutch engagement is all dependant on engine speed, get the revs up and it'll start rubbing plates... can't think how it'd work otherwise... but would be kicking myself if I start pulling things apart to find out I got this wrong.

Cheers,
Dave

[duffman]

Or would you need to start revving the engine to make the centrifugal plates move into contact, where they'll then grab, spin the engine up to speed, and then you'd start getting engine braking?

This.

You'd get some engine braking, but as you slow you'd get to a speed where the clutch lets go and you free-wheel.

[TrumpyDave]

Many thanks dude

[Crashlington]

engine braking happens even at low revs
you can even bump start these bikes by rolling down a hill and simply slamming it into gear.