I put mulching blades on my Husqvarna riding mower 48" desk and wonder whether there's a part to keep the grass from blowing to the right of the deck.

Any debris on top of the deck e.g. thumb sized mulch, driveway stones, pencil diameter sticks or larger. All may cut and snap a belt if they get wedged between the belt and any of the pulleys.

Any hard foreign object of the size that will jamb into a pulley v groove.

Is this a centre rear discharge mower, if so has the mulch plug been left in? if so this will block the outlet chute, most mowers are fairly simple in as much as the blade cuts the grass and the wings on the blade tips create a draught to send the cut grass into the bag, any blockage in the chute will stop the grass being sent into the bag, insufficient engine rpm will also effect bagging, wet grass will tend to block the chute as well.

or you sure blades on right sometimes hard to tell if yes you have bad bearings

if you have the right side you just bolt them on to the shafts

do you have the right blades for bagging ?is the deck belt slipping?

I too have had that same problem. I found that "old" blades when repeatidly sharpened and worn will cause the same problem, also aftermarket blades instead of original manufactures recommended blades may not be dimensionally correct, too short. I have had to go back to using original blades to correct the problem.
This should work for you.
Good luck.

There are a couple of things going on here. First, the blades are likely worn out and need replaced. As they wear and loose some length they can leave a trail. Second, if you have regular blades on a deck configured (by having discharge plugged) for mulching and you are using regular blades, then you can have a problem with build up. Third, you can have clumping problems if the grass is not dry when you are mowing.

I hope this is helpful for you.

yes that is most likely the cause of it, also, you have to cut more often when mulching, and the higher the cutting deck, the more likely the grass will blow out without getting mulched enough. More than likely, the blades are dull, and/or the grass is too high, or possibly even wet if it is high.

the mulching blades usually have serated lifts or a second sharp edge closer to the center of blade and is usually humped hope this helps

The only way to shred the grass while mowing is to have a pair of mulching blades on your mower, they work, but they wear out fast. They do in Florida anyway with all the sand. And don't for the grass to look a hayfield to mow it. You have to keep at it. Hope this helps.