1/ at low revs when running light the constant change from drive to overrun causes the coupling to slap to and fro in its own backlash and -
2/ At high power transmission combined with minute loss of traction the coupling whips back to the overrun position causing the bang and immediately takes up the backlash again when the bang can be repeated several times till driver reaction or road surface change breaks the cycle.
The noise is probably generated by the sudden take up of slack in belt or, in my case chain, final drive, which is why so many seem to think it is the belt jumping over the sprocket teeth and also why the noise is less when the drive belt is run very tight....
Seems a reasonable theory. But why don't all M3W owners experience it when their rear wheel loses traction? Perhaps we need to correlate bangs with tyre type?
Or are most drivers more sedate / driving bath chairs?
