The bearing assembly in your motorcycle's headstock is the only thing securing the front wheel, fork, and handlebar to the rest of your motorcycle. Seems like pretty critical component, right? Odds are, however, that those stock steering head bearings are the old-fashioned spherical variety, offering just a few dozen tiny contact points to support some serious cornering and braking loads.
Roller bearings, like the ones I installed during a recent frame-up restoration are a superior alternative. These bearings use cylindrical rollers and conical races rather than spherical balls and cupped races, providing more surface area that allows the roller bearings to handle higher loads. That extra surface area also makes roller bearings easier to adjust, so you'll spend less time looking for that tensional 'sweet spot'.
Good quality aftermarket roller bearings are more durable, too, which means less frequent adjustment down the road. You need to understand that motorcycle manufacturers use materials which fit within the budget, which often means they not the best quality money can buy. Installation of new roller bearings was straightforward, and expedited by applying the principles of thermodynamics to heat the frame and chill the races so the parts slipped together easily.
New bearings aren't the kind of exciting upgrade you'd pull your motorcycle apart to install, but if you already have your front end disassembled or need to replace your worn-out stock steering head bearings, then upgrading to aftermarket roller bearings is a no-brainer.
Head stock bearing replacement kits are are priced in line with factory replacement parts, easy to install, and come often with double-lipped weather seals. For most modern motorcycles you can find head bearing replacement kits online, or you can contact your local SKF bearing dealer to see if he has them on stock or can order them for you...