Husqvarna YTH21k46 motion drive belt pops off input pulley located under transmission cooling fan when clutch is engaged. Should I be able to rotate the input pulley by hand when the freewheel control is in the disengaged or engaged position? Could transmission be locked-up?

If hydros are in bypass (bypass rods pulled rearward and locked) the drive wheels are free to turn and you should be able to move the machine by pushing manually when brake is OFF.

If hydros are engaged (bypass rods unlocked and forward) the wheels will not turn when you attempt to move by hand.

See operators guide http://www.husqvarna.com/ddoc/HUSO/HUSO2012_NAen/HUSO2012_NAen_RZ4623_115457827%20Rev%20B.pdf

If you confirm you can manually move the mower when in bypass you can't move machine when hydros engaged, then likely an issue with the pump drive belt. This belt wraps around both hydro pumps, upper engine pulley (above the electric PTO clutch), and a tensioner pulley.

If both hydro pump cooling fans are spinning when engine is running then the pump drive belt is in place and the problem is elsewhere.

The drive belt goes around the transmission pulley (located under the cooling fan) then attaches to the engine. You will then need to loop the around the idler set. You will find a "v" shaped pulley and a flat pulley. The flat fits on the outside of the belt and the belt fits down into the "v" pulley. You need to remove the tension of the idler set to fit the belt.

To replace EZT belt
Park the mower on a level surface. Engage the park brake.

EZT belt removal
NOTE: Be careful not to damage the fan blades on the EZT as this can affect cooling or damage the EZT.

1. Remove the deck belt
2. Create slack in the belt by pushing the spring loaded idler arm away from the belt.
3. Rotate arm to release belt tension.
4. The belt should now be able to be removed from the engine pulley and EZT pulleys.

Belt installation

1. Wrap the EZT belt around the EZT pulleys.
2. Wrap the belt around the engine pulley.
3. Route the belt around the inside of the idler pulley while keeping tension off the belt and then slowly the idler assembly afterwards.
4. Check that the belt is on all the pulleys correctly and test drive your unit.
5. Afterward then re-install your mower deck once your are satisfied with the drive installation..

when you actuate the "engage blade" lever, two things may occur,
First, a mechanical action, a spring moves to put tension onto the belt.
Second; at the end of its run, actuate a switch (PTF switch) to engage the clutch that moves the pulleys that consequentially move the blades.
if the tensioner is not moving , check if spring has come lose, undone or broken, (more likely in your case) or check the PTF switch.
any other assistance, contact me, good luck.

If you need further help, reach me via phone at https://www.6ya.com/expert/gerardo_79638d1eac6a0a1f

Its pretty straight forward to fit the cable, if it is not pulling the jockey hard enough into the belt it is more likly the belt is incorrectly fitted or has stretched.

I had this same issue. New belts and correct routing did not solve the problem. The issue with my mower was the tabs that come off the frame that you bolt the transaxle (the drive for the rear wheels and axle) had almost completely torn/cracked away. This allowed the transaxle to tilt forward under a load and slip the belt off the rear drive pulley. You see no mention of this at the dealer or company sights. The tabs are so thin this is going to happen, in my opinion, in time. I reinforced this area with 1/4 inch angle iron and have had no further belt issue.

i had a 2148. you remove the mower deck as the first step. feed the belt over the pulley on top the transmission, then put it over the engine pulley. then have someone push the clutch pedal in so the tensioner pulley moves, put the belt in the guide pulley and on the tensioner. release the clutch put the deck back on and you are good to go. notice there are little keepers welded to the frame for the front, engine, pulley and it is easy to mistakenly put the belt over them instead of under them.

a general rule is that a pulley shaped like a Vee takes the V of the belt whilst a pulley which is flat takes the flat back of the belt. if you bear that in mind you will not have a problem putting belts back on. also there is a little decal on top the deck showing how the deck belt and deck drive belt go.

There should be a pulley that the brake/clutch petal pulls against to disengage. You could have a problem with that. You will have to turn it by hand to check and see. Check the main drive belt while you are in the area. It may be helpful to remove the deck so you can slide up under there get a good look.

I hope this gets you going.

First check the belt.Make sure it is tight when the lever is engaged,and the engine is off.Make sure the belt is on all pulleys,and inspect for frays in the belt.If the belt is ok then,run your hand under the fender around the area of the lever.Make sure there is no debris blocking the lever from fully engaging.If that is good.Next inspect the linkage between the lever`s handle and the deck.Again make sure there is no debris and all connections are snug.

husqvarna yth20k46
drive belt came off
fix
transmission boltes were not installed
replaced fix problem