Riding mower makes noise and has a vibration when I engage mower blades and throws the belt off

SOURCE: BLADE DRIVE BELT ADJUSTMENT

Well, most riding mowers have a "pully idler", meaning once you have the belt on there (and it is the RIGHT size), the idler automatically gives the belt tension when you engage it (in fact, the idler pully is what IS engaged when you engage the belly mower).

Couple things to check (super simple):

The Belt. Look to see if she is wore smooth out.
Sometimes....they WILL stretch on you, instead of busting/coming apart, and give you noise (when she is engaged, but wore out enough to flop around a little)

The Deck Blade Bearings. Straight away, that is what it sounds like, or bent blades.

Check your Blade Bearings (super simple):
1. Pick up your deck to the highest high setting (mower off, just sitting).
2. Reach under, and grab your mower blade (do this for both sides), and TILT your blade UP (meaning, don't LIFT the blade straight up).
Seriously, jiggle it at a TILT. If you feel some slack in the bearing, the bearing IS shot. Straight up and down is most of the time OK, IF it is VERY little play on your blade bearings. As you do it, look at your belt pulley directly on top, if you see that pully bobbing....

However, if you grab one side of the blade only, then tilt the blade up, and she moves.....
Bearings need replaced, both the upper AND lower bearings PER blade.

They are not hard to replace, and not expensive either! (Though unfortunately, most are "sealed" junk nowadays!)

Bad Bearings show up (make themselves known) in only a few ways: Tons of Noise (grinding, squealing) & Vibration.

Go check them thar Bearings!

SOURCE: Knocking in mower deck or belt clutch when engaging blades, motor bogs / slows down

YOU MAY HAVE A BENT BLADE OR EXESSEIVE BUILD UP UNDER THE DECK

Wade Mobley

• 513 Answers
• Posted on Jun 28, 2009

SOURCE: Craftsman riding mower blades will not engage

maybe the safty switch under seat might be starting to go out if that switch doesn't work the blades wont come on at all for safety

SOURCE: Mower stalls when engaging blades

check the safety switch for engager could be bad,, hope this help,, good luck

SOURCE: I have a troy bilt riding mower blades will not engage in the 1 or 2 deck setting

There is a spring attached to a tensioner that probably came unhooked while changing the belt. Higher deck settings push the deck backwards enough to spin the blades, the lower setting need the spring tensioner to take up the slack in the belt.