Greg58 may have figured it out; but if not and If I am understanding what you are saying:
Engine is off. Clutch hand lever is all the way out, in the "drive" position like you would have it to travel down the road under engine power.
You are in your driveway with the engine turned off and the bike rolls around with little rolling resistance like the clutch and engine are not connected anymore.
There are 3 places that can fail and cause this.
1. Engine chain sprocket.
2. Clutch hub.
3. Crankshaft pinion gear.
Each assembly has what is called a "woodruff key" that locks the rotating part to the shaft that it mounts onto.
If the woodruff key shears, the rotating part will be allowed to rotate independently from the shaft it once was locked to.
Each assembly is held together by a nut and lockwasher. If the nut comes loose it will create a sloppy fit and the woodruff key will get sheared.
Check them all, I bet you will find one of them affected.