as grizz1 said put a shim between the clutch nut and the inner bearing..
DO MAKE SURE THIS IS LESS THAN 10MM DIAMETER.proper clutch shims are usually sold in packs of 3 thicknesses.5x8x 0.1,0.2,0.3..I can't tell you how often I set up clutches for guys at the track who have just slung any old washer in there.or one of those huge ones kyosho and others used to fit on old style 2 shoe clutches to stop the shoes rubbing on the bell..
THE SHIM MUST TOUCH ONLY THE INNER RACE OF THE BEARING.if it is 10mm or larger it will rub on both the inner and outer races as the bearing turns and you will get friction,heat then either the washer will disintegrate or the bearing or both..slide the clutch bell and bearings on top of the shim and look at how much the crank end protrudes beyond the outer bearing.If it looks like 1mm or more you would be better to add a shim between the flywheel and the motor's front bearing.These are usually at least 1mm thick and better for large adjustments..once the crank is only protruding maybe .5mm or less check to see you have some clearance between the clutch shoes and the inside of the clutch bell.(if you don't use ventilated bells you have to guess this on feel)if there is a lot of clearance you are better to fit a thinner shim between the clutch nut and the inner bearing and thicker shims under the bell retaining screw.if it looks like the shoes are almost touching the inside of the bell then increase the shim thickness inside and less or nothing under the outer screw.I usually shim till I get a tiny amount of drag when spinning the clutch bell then remove .2mm..the difference should be obvious when you spin the bell by hand unless you fill your bearings with thick grease.(I do..
)
I don't have a diagram but that pretty much cover it...