Farmall Cub

I have a 1965 Cub with a belly mower. When I hit heavy grass when mowing, the belt begins to wobble and soon pops of the drive pulley. How can I address this problem? Are there standards for alignment of the mower and belt drive pulleys? Has someone found a way to reduce or eliminates the wobble in the belt?

If the belt wobbles and has been thrown off the pulleys it is likely that some of the cords have been stretched and / or broken. Consider replacing the belt. As far as pulley alignment goes, try to adjust the idlers so the belt aligns well with the driven pulley evenly both on entry and exit.

But keep in mind that the entry is MUCH more important than the exit. The belt should approach each pulley well centered and square with the world. If the belt has ever been accidently turned so it runs sideways without being thrown off, if can't be trained to run normally. For some applications, Woods belts have a full twist built in to run in the place where flopping is more likely. This causes the flopping to cancel itself. This is IMPORTANT!