Having to stop your mower and reinstall your deck belt is an inconvenience. When your belt continues to come off your Bad Boy mower deck it can become very frustrating. I have listed some items to check below that can cause the belt to come off your mower.
A Bad Boy lawn mower deck belt may keep coming off the mower deck because the deck belt is worn, or shredded; bearings failed in the pulleys or spindle housings; belt tension is incorrect; debris interfering with deck components, or the belt is covered in grease or rust.
Always take safety precautions when working with your Bad Boy mower deck. Remove the ignition key, disconnect the spark plug boots and protect your hands from sharp objects.
Never work on your mower until all moving parts have stopped. Refer to your owner’s manual for additional safety features on your mower.
This post may include affiliate links. Purchases made through these links may provide a commission for us, at no extra cost to you. As an Amazon Associate, we earn from qualifying purchases.
Follow all safety instructions provided in your equipment operator’s manual before diagnosing, repairing, or operating. Consult a professional if you don’t have the skills, or knowledge or are not in the condition to perform the repair safely.
7 Reasons Your Bad Boy Lawn Mower Belt Keeps Coming Off Your Deck
Worn or Loose Deck Belt
A mower deck belt will wear and stretch over time from normal use. When the belt is not in good condition, it can roll off your pulleys and keep coming off your deck.
Inspect your belt for signs of wearing. These signs include a glazed shiny appearance, stretching, and cracking.
Other signs are when your belt sits deep in the grooves of your pulleys or it sits loose on the pulleys. When you notice any of these signs, replace the old belt with a new Bad Boy mower deck belt.
You can bring your old belt to the auto parts store to try to have them match it up, but in my experience, you don’t always get the right type, size, or quality of the belt.
I prefer to purchase OEM (Original Equipment Manufacturer) belts from a Bad Boy dealership as they are of high quality and of the right material so your mower operates at its best. They also tend to last longer than a non-OEM belt.
Shredded Deck Belt
A belt can become shredded causing it to become weak and more likely to break. The most common reasons a belt will shred is from incorrect installation or from rubbing on a bracket that has moved out of place.
If you find your belt is shredding along its edges, first check to make sure you are using the right belt and it is correctly routed around your deck pulleys.
You may have a decal on your mower with a diagram that shows the belt layout. If you can’t find it, don’t worry. Refer to your Bad Boy owner’s manual or a parts diagram to get this information.
Once you have confirmed your belt has been installed correctly. Check for any brackets that your belt may be rubbing against once your mower deck is engaged.
You may find a shiny wear spot on a bracket where the belt continues to rub. Adjust any brackets you find causing your belt to rub so they no longer rub.
If the bracket you are adjusting has a bushing in it, the bushing may need to be replaced. You must replace a bracket you are unable to adjust to prevent the belt from rubbing.
Lastly, replace the mower deck belt with a new one once you have confirmed there are no more points on your mower deck the belt is rubbing against.
Bad Bearing in Your Spindle Housing
A bearing may be bad in your zero-turn spindle housing assembly. This is the piece on your deck that the mower blade attaches to. A bad bearing can cause your blade to wobble because there is an extra movement where the blade attaches.
At high speeds, the wobble can cause an excessive vibration that can knock the belt off your zero-turn.
To check for a bad bearing, access the underside of your mower deck. Protect your hands and grab a hold of each end of your mower blade. Rock the blade up and down feeling for movement or hearing a noise.
If you find your blade is secure to the cutter housing, but there is extra movement or a knocking sound, remove your blade and disassemble your cutter housing assembly.
Chances are highly likely you have a bad bearing in the housing that must be replaced. Some models allow you to replace only the bearing while others require you to replace the whole cutter housing assembly due to the bearing being sealed.
Bad Bearing in Your Pulley
Each pulley must be sitting flat and parallel to the mower deck. It should be attached securely to the deck and there shouldn’t be movement where one side of the pulley is higher off the deck than the other side.
When a belt runs across a pulley that isn’t sitting flat, it can cause vibration and the belt can come off.
Check each pulley by slowly spinning the pulley by hand. When you feel resistance or hear a noise coming from the bearing, the bearing is bad. The pulley must be replaced.
Insufficient Tension on Your Mower Belt
Tension must be put on your belt to keep your belt from falling off your pulleys. You will find a tensioner spring on your mower. Too much tension can cause damage to your deck components while too little tension can cause the belt to slip or come off your Bad Boy mower.
Check your tension and make the necessary adjustments using a belt tension gauge. Most Bad Boy mowers require the belt tension to be 70-75 lbs. Refer to your model’s owner’s manual to find the tension specification for your mower.
Some models require you to slide the bolt on the deck to adjust the spring tension while others require the loosening of jam nuts to adjust the eye bolt to the tensioner spring is attached to.
Recheck the tension after you have run your mower for about 30 minutes to ensure it is still correct.
Debris Stuck in the Grooves of Your Pulleys
Debris and dirt can get caught in your pulleys causing your belt to have to stretch around the extra material.
When this happens, the belt may roll off the pulleys and come off your mower or it could snap from the extra stress on the belt. Clean the pulleys removing any dirt, stones, and grass that pack in the pulleys or under the pulleys.
Oil or Rust on Your Mower Deck Belt
An oil leak that leaks onto your Bad Boy deck and pulleys can get on your deck belt and cause it to slip off your pulleys.
When oil sits on your belt for extended periods of time, the belt can swell. Repair the oil leak and clean the oil of your deck. Replace your deck belt with a new belt.
Rust causes your belt to dry out and become more likely to crack and break. Clean off the rust from your deck and components. Replace pulleys that are very rusty. Those that you aren’t going to be able to remove all the rust. Install a new mower deck belt.
Still Experiencing Problems with Your Bad Boy Zero Turn Mower?
Own a lawn mower long enough, you’ll start running into problems with it starting, not continuing to run, smoking, leaking gas, giving a bad cut, vibrating, or another issue.
To help you save time and money, I have put together a guide to help you troubleshoot the next problem that develops on your mower.
You can find this guide at Common Bad Boy Lawn Mower Problems & Solutions.
If you are unsure how to perform diagnostics and repairs on your lawn mower safely, it’s best to have a professional complete the repairs.
This will help you avoid personal injury or additional damage to the mower. Your local Bad Boy lawn mower dealership or lawn mower repair shop will be able to help you solve your problem.