"When tightening the nut for the rear wheel you tighten it to around 90 ft./lbs. torque. In this case, you are NOT putting any load on the bearings. you are tightened the hub and inner race against a shoulder on the main shaft. The clearance of the main bearing on the rear wheel main shaft of the Bajaj engine is fixed. No matter how loose or tight you make the nut, the bearing clearance will remain the same."
This is critical as the rear hub nut holds the rear wheel onto the splined drive shaft. If this hub nut comes loose, there is a good chance that you will strip the drive shaft splines necessitating a major engine repair. 2003 and later models had a slightly larger drive shaft with slightly more robust splines. This was one of the few changes made after the modern Chetak hit the American roadways, the American riders spent more time at higher speeds placing higher forces on this splined shaft. The other major change involved a larger CDI as the American riders had the mandatory "head-light on" federal requirement that the 2002 CDI could not keep up with.