Why Does My Riding Lawn Mower Keep Breaking Belts?

Why Does My Riding Lawn Mower Keep Breaking Belts?

Does your riding lawn mower keep breaking belts? A good belt should last several seasons, so if you’re replacing them annually, or more, let’s find out some reasons. Better yet, let’s talk about how to fix the problem.

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Belt Function

This depends on what kind of belt we’re talking about, but the function is essentially the same – the transfer of power.

Some machines use a drive belt to provide power to drive (duh!) the machine. More commonly when we’re talking about belts is the mower deck belt which transfers power to the mower deck.

If the belt is missing or not performing adequately, there can be improper, or no cutting at all.

So if you find yourself frequently replacing a belt, what are the possible causes?

Grass Debris

Grass debris can cause a whole host of problems, and that’s why it’s really so important to properly clean your machine.

Among other issues created by grass debris is the potential to break belts. This is for a couple of reasons.

First, as the debris builds up, it can actually work its way between the belt and form to the pulley. This essentially creates more tension to the belt and stretches it.

This little bit of added tension can be enough to snap the belt, although that’s probably infrequent.

More likely, if grass is the culprit, is damage to the spindles. As the grass sits on the deck, it holds in the moisture that was in the grass. That moisture leads to rust and eventually seized spindles.

Seized Spindles and/or Bearings

If the spindle is seized, then the belt is just slipping on the spindle. As the belt slips, it quickly heats up and then fails. 

If this is the case, chances are that you recognize other symptoms: a horrible whine coming from the mower deck and inefficient or lopsided cutting.

Spindles don’t just seize overnight, but if it’s a junk machine like I usually pick up, make sure to test the spindles before running the machine. They should turn freely, and the bearings should not “growl” when turned.

Remember, as part of your routine maintenance, you should be applying grease to the zerks on the spindles to keep them properly lubricated.

Defective Wear

This actually happened to a coworker of mine last year. He had just bought a brand new riding lawn mower and went through three belts in the first week.

He asked me what I thought about that, and I assured him that it was not normal.

After closer inspection, he determined that one of the belt guards was bent and was contacting the belt. This quickly frayed the belt so they failed quickly.

If you find a lot of belt debris on the deck, take a good look at the path that it’s traveling. Make sure that the only contact points are on the pulleys and that nothing else is impeding its travel.

Recap

If your riding lawn mower keeps breaking belts, know that this is not common and something is certainly wrong. The good news is that there aren’t really a lot of possible causes, so you should be able to quickly identify what is causing the problem.

Did I forget something? Let me know in the comments below.

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