BBT 4 Speed Self Propelled Mower Catcher

I purchased this mower some years back. Although the unit is quite heavy, it has performed as expected apart from the auto drive only operating at one speed. Recently the end of the auto drive cable pulled out and I needed to address how to replace it, after ordering a new idler assembly, cable and drive belt. Once the underside of the deck was exposed the problem proved to be a completely rusted and ceased idler assembly. Both idler wheels were also ceased and badly worn. There is a "Pope" fitting on the top of the deck which allows a water hose to be connected supposedly allowing water pressure to "clean" the idler assembly area. Looking at the idler wheels, on the new assembly, I noticed that the 6000 size bearings are the same, substantially, unsealed types as originally supplied. Also, the bearings have been "molded" inside the idler wheels which does not allow the immediate replacement of the bearing with more suitable sealed type. Although you can purchase both the complete idler assembly and the individual idler wheels my feelings are that, the failure I experienced, will continue to occur. My suggestion is that the bearings, being supplied, should have seals that completely exclude any moisture ingress into the bearing race, hopefully increasing their service life.