Drive side bearings


How to increase the longevity of your drive side bearings. You may note that when you strip the bearings out of your drive side case that the spacer is usually rusty, possibly indicating that the drive side bearings may be surviving on the minimum of oil. BSA probably intended it that way as the sealing on these bearings is quite rudimentary. You will notice that there is a small drain hole from the bearings, but no real way of lubricating them (relying on the crankcase pressure from the falling piston to put a mist on them which isn't helped by the valve on the crankcase letting some of the pressure out) What you have to do is remove the bearings, then blank off the drain hole with epoxy resin or Araldite and drill a similar hole on the top aiming at the cavity between the bearings, its quite a big gap so you shouldn't miss! You can then open out the top of the hole with a Dremel or a countersink to form a funnel shape, don't go too deep or you may weaken the crankcase! It may help you to do this first as then it's easier to start the drilling. Then get a replacement outer main bearing with a seal on one side place this in the crankcase with the seal on the outside and the replace the inner bearing and spacer. Job Done! You can then jettison the oil flinger on this side of the flywheel. This allows the oil running down the crankcase wall to funnel into the main bearing cavity and not allow it to run out until it reaches the top of the outer race on the bearing, thus keeping a bit more oil around the bearings and hopefully increasing their life!