LX277 drive belt loose

[phoogles]

I replaced all of the pulleys, the deck belt and now just replaced the belt that goes from the PTO clutch to the double deck pulley in the back of the deck (i *think* that's called the drive belt).
The PTO is engaging properly but the belt slips after a few yards of mowing. It's on correctly before mowing. I read on a site that it could be the idler arm bushing is worn. That's cheap enough to replace but I'd like some feedback if that sounds like the problem.
The belt was on tight but when i look after it slips, the double deck pulley in the back has moved forward, loosening the belt.
Any input would be greatly appreciated!

Thanks!

It's part 46 on the lx277 schematic
I'm not sure how to add pictures

 

[tomplum]

48C deck? I would refer to it as the primary deck belt. Bushings for the tensioner will usually get to the point to where they won't allow the arm to move freely. It all has to pivot freely to work well. A bugger to wrestle off and clean up. But as you said the bushings are cheap. Other issues?

 

[Jimmy Joe]

I replaced all of the pulleys, the deck belt and now just replaced the belt that goes from the PTO clutch to the double deck pulley in the back of the deck (i *think* that's called the drive belt).
The PTO is engaging properly but the belt slips after a few yards of mowing. It's on correctly before mowing. I read on a site that it could be the idler arm bushing is worn. That's cheap enough to replace but I'd like some feedback if that sounds like the problem.
The belt was on tight but when i look after it slips, the double deck pulley in the back has moved forward, loosening the belt.
Any input would be greatly appreciated!

Thanks!

It's part 46 on the lx277 schematic
I'm not sure how to add pictures

You say the pulley moves forward, is the tension arm placed correctly in the notch in the deck housing. Are you sure the belt for the pto is slipping and not the deck belt, if you just changed the pulleys make sure they are the right diameter. Did you have any issues with the belt slipping before you replaced the parts?

 

[Spanner]

Agree - Is lever locked in notch?
Also, did you fit the double pulley the right way up? The two sheaves are different diameter. (Smaller on top, except the 42"C deck)
Which deck do you have??