Are the blades hitting the deck or each other?? when you put the timing belt in, you have to put the blades perpendicular to each other. If you are looking straight down on the deck, one blade should be north and south, and the other one east to west. That is how youu put them in time. If your blade is hitting the deck, I would suspect that you have some blown bearings in the spindle, hence this is maybe why the timing belt broke to begin with!
The mower does not have timed blades. They should never hit each other no matter where they are. I think the problem is a bad spindle bearing. Or the wrong blades are installed that are too big.
