How To Repair the Drive Belt on a Riding Lawn Mower
For the do-it-yourself homeowner, here are some step-by-step instructions on how to change a riding lawn mower drive belt. These instructions are specifically for a 700 Series riding mower. Depending on your model, the steps to install lawn mower belts may vary. If you are uncomfortable with this procedure or don't feel qualified to replace your riding lawn mower drive belt, please contact your Authorized Service Dealer for drive belt replacement.
Always observe safety rules when performing any lawn mower maintenance. Safety glasses or goggles, and hand protection, in the form of mechanic gloves, should always be used.
Before starting this project, make sure you have the correct lawn tractor parts. Use our Part Finder to look up your belt based on the part numbers for your riding lawn mower. The V belt found on your tractor is specially designed to engage and disengage safely. A substitute, or NON-Original Equipment Manufacturer (OEM), V-belt can be dangerous as it may not disengage completely. For a proper working machine, always use factory approved lawn mower belts.
It's a good idea to take a picture of how the lawn mower belts are routed before removal. During the installation process, you can refer back to the pictures for reference.
Note: Because there is inter-play between the two drive belts in the variable-speed pulley system, it is a good practice to replace both riding lawn mower drive belts at the same time.
Step 1: Position the mower to change the lawn mower belt
Place the mower on a flat, level surface and set the parking brake to keep the mower from rolling while you're working.
Step 2: Check the engine temperature before replacing the lawn mower belt
If the engine is hot, allow the exhaust system to cool down before attempting any maintenance.
Step 3: Detach the spark plug wire
Open the hood and remove the spark plug wire(s). Ground the spark plug wire (s) against the engine to prevent it from starting during lawn mower maintenance.
Step 4: Remove the cutting deck and battery
Remove the cutting deck. Instructions for removing the cutting deck can be found in your Operator's Manual in the "Service" section. Then lift the seat to gain access to the battery. When disconnecting the battery, always disconnect the black negative battery cable first, and then disconnect the red positive battery cable.
Step 5: Loosen the transaxle pulley
Look down through where the battery was located. You will see a large transaxle pulley. Loosen the large nut holding the pulley to the input shaft using a 7/16" socket.
Step 6: Relieve tension on the upper drive belt
Disconnect the spring from the anchor bolt on the left side of the tractor using a spring puller or a small piece of rope. This will relieve tension on the upper drive belt. Note: Orientation of left and right is determined from the operator's position in the seat.
Step 7: Remove the upper drive belt and lawn mower belt guide
Maneuver the upper (rear) belt from the transaxle pulley and remove the belt from the mower. Next, remove the belt guide from the variable speed pulley bracket using a 1/4" socket. Note: These are all accessed through the battery compartment.
Step 8: Take the belt off the variable speed pulley
Lift the middle sheave slightly so the lawn mower belt will clear the belt guide, and slip the belt off of the variable speed pulley.
Step 9: Remove the belt keeper
Remove the belt keeper that surrounds the engine pulley using a 1/2" wrench.
Step 10: Remove the bolt securing the crankshaft pulley
Remove the bolt securing the crankshaft pulley using a 5/8" socket. Note: The use of an air impact gun is recommended for removal purposes. If not, use a strap wrench to hold the crankshaft pulley while loosening the bolt.
Step 11: Make a note of where parts are located before you install a new drive mower belt for your riding lawn mower
As you remove the engine pulley, note the orientation of the parts for reassembly (or take a picture). The pulley is secured by a bolt, lock washer, and a heavy flat washer. A spacer is positioned above the pulley on the crankshaft and the top edge radius matches the step on the crankshaft.
Step 12: Remove the lower drive belt from the lawn mower
Remove the lower drive belt from the mower by pulling it towards the engine.
Step 13: Install the new lower drive belt
Lawn mower belt installation is essentially the removal process in reverse. As you install the new lower drive belt, confirm the correct belt routing inside of all the belt keepers and through all the guide pins using the pictures taken before the lawn mower belt removal.
Step 14: Apply anti-seize compound to the crankshaft
Apply a very small quantity of anti-seize compound to the engine crankshaft. This will help ease the crankshaft removal in the future when needed. Note: DO NOT get any anti-seize compound on the bolt threads or in the bolt hole of the crankshaft.
Step 15: Insert a spacer
Install the spacer with the rounded shoulder towards the engine.
Step 16: Install the crankshaft pulley and bolt
While holding the spacer in place, install the crankshaft pulley. Be careful not to get any of the anti-seize compound on the belt or in the "V" of the pulley. Then, install the crankshaft pulley bolt with the lock washer and heavy flat washer in place. (The lock-washer to the bolt head and the heavy flat washer to the crankshaft pulley.)
Step 17: Tighten the crankshaft pulley bolt
Using a torque wrench, tighten the crankshaft pulley bolt, to a torque of 37.5 - 50 foot pounds (51-68 Newton Meters).
Step 18: Replace the lower transmission belt
Place the lower transmission belt into the upper "V" Pulley closest to the engine on the crankshaft pulley. Carefully lift the middle sheave slightly so the belt will clear the belt guide and slip it onto the variable speed pulley. Make sure the lawn mower belt is fully seated in the belt grooves.
Step 19: Re-install the lawn mower belt keeper and belt guide
Re-install the belt keeper surrounding the engine pulley, using a 1/2" wrench. Then re-install the belt guide, which was removed from the variable speed pulley bracket, by using a 1/4" socket.
Step 20: Install the new riding lawn mower upper drive belt
nstall the new upper drive belt into the upper sheave of the variable speed pulley and around the transaxle pulley. Make sure the lawn mower belt is fully seated in the grooves.
Step 21: Re-install the tension spring
Re-install the tension spring and connect it to the anchor bolt on the left side of the tractor.
Step 22: Secure the transaxle pulley
Tighten the large nut that secures the transaxle pulley to the input shaft of the transaxle using a torque wrench and torque to 10-15 foot pounds (13.6-20.3 Newton meters).
Because of the tension change when you replace lawn mower belts, it is always recommended to check all drive adjustments after changing the drive belts.
The following procedure will be for the speed control linkage on the variable speed belt drive.
Step 23: Check the speed control linkage on the variable speed belt drive
With the parking brake still engaged remove the cotter pin from the ferrule on the top side of the variable speed pulley bracket.
Disconnect the ferrule from the bracket. If you need to make an adjustment there will be tension on the linkage and the resulting friction will cause resistance as you slide out the ferrule.
Thread the ferrule up or down the rod until the post fits in the hole without any resistance.
Put the cotter pin back through the hole in the ferrule on the top side of the variable speed pulley bracket.
Step 24: Check the cruise control/parking brake adjustment on the variable speed belt drive
Again, with the parking brake engaged, remove the cotter pin that secures the ferrule in the latch assembly.
Disconnect the linkage from the latch assembly.
Adjust the ferrule with a new cotter pin as you did in Step 23.
Secure the ferrule with a new cotter pin and test the operation of the linkage.
Step 25: Re-install the cutting deck
Put the cutting deck back in place under the mower as outlined in your owner's manual. Just follow the cutting deck removal instructions in reverse order.
Step 26: Re-install the battery
Opposite of when you removed the battery, connect the red positive battery cable to the positive battery terminal first.
Step 27: Reattach the spark plug wire(s)
Reconnect the spark plug wires to the spark plugs.
Step 28: Check the operation of the new lawn mower belts
Start the unit and check that all linkage and related safety features are operating correctly before returning the mower to full operation. If while performing lawn mower maintenance on your drive belts, you noticed other issues or signs of wear, take the time to order replacement lawn tractor parts before running the machine again. Even if only slightly worn, operating with damaged equipment could cause larger issues if not addressed. If your new lawn mower belts and other parts are running smoothly, then you're ready to get back out and mow!
Fix equipment issues quickly
When you need parts for your walk-behind lawn mower or riding lawn mower, you can use the MTD Genuine Parts Part Finder to find the correct one. Common parts include:
Riding Mower Blades
Riding Mower Belts
Riding Mower Blade Spindles
Riding Mower Tires & Wheels
Oil, Lubricants and Fuel Additives
The MTD Genuine Parts Knowledge Center provides do-it-yourself instructions for performing many basic maintenance items, including replacing cutting blades, drive and deck belts, and engine oil. If you find your machine has a bigger problem, use our service locator to find a qualified MTD service provider in your area.