Have an old 21" Snapper pusher. For the first time in several years
I've decided to start bagging the grass instead of mulching it.
Problem is, I'm now finding that the grass clogs the chute in short
order. Very little actually makes it into the bag. The last time I
bagged the grass this wasn't a problem.

I tried cleaning the bag thinking maybe a lack of air flow was somehow
an issue - gave it a good scrubbing in the tub with lots of detergent.
Sharpened the blade. I found the bottom lip of the chute was splitting
so I formed some sheet aluminum to fit over the lip and pop-riveted it
in place to give the grass a smooth entry point. None of this has
helped.

Why would this now be an issue when it hasn't been in the past? Same
mower, same blade.