Those bushings break apart, melt and then stick to the back of the clutch hub, get between the hub and the clutch housing, and also clog the crankshaft lubricating hole in the gear.
Those melted sticky bushings on the back of the hub will cause drag, and getting no oil between the gear and crankshaft will also cause drag...leading to no idle.
Size is OD 11 mm, ID 7 mm, length 7 mm.
You can get the correct bushing from Treatland. You need 6.
There is a spline washer behind the hub...note which way it is facing. Normally, the flat side should face in.
You should be able to spin the clutch/hub inside the housing will no drag.
The clutch housing should turn independently of the clutch hub and the crankshaft.
Axial play should be minimal, but have zero drag. If there is excessive play, you can turn the spline washer around.
You need 13.5 oz of non-detergent oil