4' king kutter finish mower. Replaced the belt 112 when I engage the belt pops off. Seems that the idler pulley is so close to the main drive pulley it binds and the belt pops off. Need a solution.

Safety and Preparation Serious injury can occur if the engine or mower blades accidentally start while you are working with lawn tractors. To prevent this, drive the Murray lawn tractor onto a flat work surface and disengage the mowing deck cutting blades. Engage the parking brake to keep the mower from moving; chock the wheels with a wooden block or brick. Adjust the mowing deck to the lowest position. Turn off the engine and remove the key from the ignition. While not necessary, you may even wish to disconnect the spark plug wire from the spark plug. Mowing Deck Removal You must remove the mowing deck on a Murray lawn tractor to gain access to the belts. Remove the adjustment rod hairpins, followed by the adjustment rod pins from the front left and right sides of the mowing deck. At the rear on the left and right sides, pull out the retaining hairpins and slide the mowing deck suspension links from the adjuster plates to separate the rear mowing deck from the frame. Remove the blade control rod stud, including the hairpin and washer, from the top of the blade control lever shift linkage at the left rear of the deck. Remove the front hanger rod, including the hairpin and flat washer that hold the rod in place. Loosen the belt guide retaining bolts with a socket wrench and remove the engine stack pulley belt so you can slide the mower deck out from under the tractor Transmission Drive Belt Installation Slide the new transmission drive belt between the engine stack pulley belt guides, over the belt guide plate and under the engine stack pulley. Fit the transmission drive belt around the top engine stack pulley. Push the free end of the transmission drive belt up through the transmission shifter hole in the lawn tractor floorboard. Slip the transmission drive belt loop over the transmission shifter. Pull the transmission drive belt down through the transmission shifter hole. Fit the transmission drive belt around the transmission drive pulley and tighten the transmission drive pulley belt guide retaining bolts to hold it in place. Fit the transmission drive belt flat side around the idler pulley. Slide the idler pulley onto the idler pulley stud while holding the belt in place. Tighten the transmission idler pulley retaining nut with a socket wrench to secure the idler pulley to the idler pulley stud. Mowing Deck Drive Belt Installation Pull back on the right side mowing deck mandrel pulley spring-tensioned belt retainer. Guide the new mowing deck drive belt around the right side mandrel pulley and release the belt retainer. Pull the drive belt spring-tensioned retainer away from the mowing deck idler pulley, guiding the deck drive belt around the idler pulley. Fit the mowing deck drive belt around the left side mandrel pulley and under the rear mowing deck cross link rod between the right and left side mandrel pulley. Slide the mowing deck under the right side lawn tractor frame, reconnecting the deck to the frame in reverse order of removal. Engage and disengage the mower deck while driving the mower to test the belt for proper operation.

depending on the age of the machine, there could be several possibilities
1-- belts are not tight enough--- belt tension system is not correct, wrong length belts
2--bearings for the shafts for the blades are rusted up and seized - preventing the blades from moving--- switch the machine off , disengage the belt drive and see if you can turn the blades by hand
3--- if you have an electric pto system to drive the belts to the blades then that system is not getting full power to engage the PTO or the clutch is not working--worn facings
take it to a service dealer and have a proper diagnosis done

be sure it is the correct one for that mower and it is on correctly and it is from a lawn mower parts store. not one from tractor supply or rural king.

Hi scott if you can shut the mower off and jack the mower up and look past the mower deck and see if yopu can see the drive belt it may have broken or jumped off an idler pulley. If it is the drive belt you will have to drop the deck to get toit. sometiomes a belt will roll itself and cause it to run off the pulley. good luck from ron.

Hi, check the idler pulley arm and return spring on that belt. Its most likely not pivoting freely allowing the belt to loosen when you operate the clutch, regards Phil.

check that the idler pulley is assembled on the belt properly as the belt is not to run against itself at any time

Have you check the tensioners? The idler pulleys that are on the arms with springs on them. My reasoning is, if the arms are rusted, or stuck for some reason and not moving freely then the springs can't pull the belt tight. If that's the case, I could see where the belt could be slipping more than it needs to and prematurely wearing out. Just something to check. Good luck.

On most riding mowers flipping the handle to engage the blade causes an idler pulley to engage the drive belt, which takes up the slack in the belt and pulls it against the drive pulleys. A few odd-balls have an electric clutch to engage the blades.

There's a couple of things that could be causing this. First, make sure the idler pulleys and blade pulleys spin freely. Second make sure the belt is behind the belt keepers on the two idler pulleys. There is only one on the left idler, but TWO on the right idler. I suspect that is your problem. Anyway, once the belt is on, engage the blades, with engine OFF, and inspect the belt routing, making sure it's not over or under something it shouldn't be.

Pull the belt cover off on the side of the engage lever and you will see that it is not a wire cable that engages the idler pulley. It's a rod connected to a long spring. Perhaps the spring came off or is defective as it puts tension on the idler pulley against the drive belt when you engage the blades. Further, there is a return spring to pull the idler pulley away from the drive belt when you disengage the blades. Check all the connections for the springs and see that the engage lever is mounted tightly. Also check the idler pulley itself.