MTD Ride-on Mower: blades don't stop

This one is driving me nuts.

Now, I'll readily admit I pulled this thing out of the trash. Well, not trash, but it was curb-side with a sign on it that said "FREE!". It's an MTD 38" cut with a B&S 12.5 HP engine.

I used it all last season. It starts and runs great. I had to put a muffler on it, which I did on the cheap with a big-box store universal muffler and a piece of black pipe (so it's a little loud).

The problem with it is that the blades don't stop turning. When I pull the blade control back to the STOP position, they're still turning. Not with as much vigor as when they are fully engaged, but enough to put a hurtin on you.

It seems to be a really simple arrangement. There's no idler pulley or anything. Just a belt that goes from the engine crankshaft to the blades. It appears to me as if when you drop the deck, that puts enough tension on the belt to drive the blades. When you put the deck up, the belt gets loose and the blades should stop. They don't. The belt gets loose, but they keep spinning.

Is it as simple as a new belt?

If it helps, the model number is 13AH660F000.

 

Could be the belt if it's not the right one, or it could need new blade brakes (bolted under each footrest).

 

I thought maybe someone put the wrong belt on it, but it does loosen up like it should.

Blade brakes sound interesting. What do they look like? Are they part of the blade transmission assembly?

EDIT: Found them. Mine don't appear to be contacting anything, and one is missing. I'll have to investigate further.

Thanks!

 

Install the missing one, then you can adjust the linkage that pulls the deck up to get it a little higher so that it contacts the brakes.