Gday dontknowitall,
Yup, this stage can be a problem!. The key thing here for me is to get some quite coarse emery cloth and get all the rust and paint off the shaft. The bearings are a snug slip fit and any rust or paint will stop them sliding. Heat from a hot air gun on the bearing may help-and of course liberal use of the penetrating oil of your choice. That said Iβve often resorted to surgical techniques. The bearings and flangettes are dirt cheap and not worth trying to save and if fact itβs wise to replace them anyway when the opportunity arises. The key here is to butcher the bearing and not any other bits you are trying to use
Fatigue failure of the shaft at the sprocket is not new. A couple of my donors have shafts broken in the same place. Obviously there is a concentration of load there and the axle metallurgy has been altered by the welding but I wonder if there are other contributing factors such as the axle being bent at some time in the past or the axle not being adjusted true (square) for an extended period.
Iβm not sure i can advocate a welded repair as a long term solution without some sort of flanged repair sleeve or the like. Problem with that is the close proximity of the bearing. I have thought about using a 1β bearing, turning a step in the axle, sliding on a fairly long flanged bush so it stays true when welding etc, etc,......much easier to get a replacement if you can.
Check any replacement axle is not bent.
Cheers,
