I have a mtd 19931s rear discharge deck . I bent a sprindle so I replaced both,all bearings and the $140 cogged belt. Now the blades won't stay timed. It all looks so simple that I'm at a loss and ran out of guesses. thanks for any ideas.
I'm not familiar with your model deck, but if it is driven by a "V" type belt like 99.9% mowers are, there is no need to "time" the blades, they are desiged to miss each other by having one slightly in front of the other. Only decks that need to be timed are driven by gear belts (have gear teeth molded across the width of the belt).
The old Wheel-Horse we had when I was a kid had a timed, rear-discharge deck. As I recall, there was a shaft with bevel gears to keep the blades in time. The bearings or gears were worn enough that it would jump time, so we didn't use it.
It did have a front-mounted sickle bar that we used to mow rough terrain with, however.