Personal view The sprocket nut is there to stop the sprocket sliding off the output shaft. It doesn’t need to tighten flush with the sprocket to do this. The output shaft is the fault on some of the fazers. The grooves in some output shafts are cut slightly too wide. This allows the sprocket to move backwards and forwards on the shaft when placed under load or off load. Because the nut is tight against the sprocket it continually rotates slightly on the threads… wearing them out. The answer in my opinion is grind down the flange on the sprocket nut so that when it tightens on the shaft it is simply flush with the sprocket but does not tighten against it…. And put some grease on the sprocket to further ease the junction between the nut and sprocket. Therefore there is insufficient ‘grip’ between the sprocket and the nut so it doesn't turn the nut. In essence you want to tighten the nut up on the output shaft but not tighten it up against the sprocket.
Personal view The sprocket nut is there to stop the sprocket sliding off the output shaft. It doesn’t need to tighten flush with the sprocket to do this. The output shaft is the fault on some of the fazers. The grooves in some output shafts are cut slightly too wide. This allows the sprocket to move backwards and forwards on the shaft when placed under load or off load.
Because the nut is tight against the sprocket it continually rotates slightly on the threads… wearing them out. The answer in my opinion is grind down the flange on the sprocket nut so that when it tightens on the shaft it is simply flush with the sprocket but does not tighten against it…. And put some grease on the sprocket to further ease the junction between the nut and sprocket. Therefore there is insufficient ‘grip’ between the sprocket and the nut so it doesn't turn the nut. In essence you want to tighten the nut up on the output shaft but not tighten it up against the sprocket.