Lawn Mower Grass Catcher Troubleshooting

Stopping every 5 minutes to clear the underside of the mower isn’t much fun! Grass catcher problems can be so annoying.

Troubleshooting a lawn mower grass catcher? Common grass catcher problems like, clumping, clogging, uncut grass, and a grass bag that won’t fill are caused by:

  • Grass Too Tall/Wet
  • Deck Too Low
  • Dull/Damaged Blade
  • Deck Grass Build-up
  • Throttle Too Low
  • Moving Too Fast
  • Poor Engine Performance 
  • Damage To Deck
  • Deck Belt Slip (Tractor) 
  • PTO Slip (Tractor)
  • Wrong Blade Type
  • Grass Bag Matted

In this guide, I will cover all the most common grass catcher problems and the solutions.

Very often a bad or blunt blade is the root cause of bagging issues. Sharpening or replacing a worn blade will improve bagging performance.

If you need more help, check out the “Blade sharpening video”.

The sharpening video covers safely sharpening the blade both on and off the mower. It also includes balancing the blade and torquing the blade bolt to specification.

What Is Mulching?

I live in Ireland and it rains, a lot, sometimes it rains persistently, and if you need to cut grass, then you have to cut wet grass. Grass chute clogging is usually caused by cutting conditions but is also commonly caused by a worn cutting blade.

The blade is the business end and it needs to be in tip-top condition. 

Chute – A clogged chute can of course be a symptom of an underlying problem. So clearing the chute may not solve the problem. Check the chute for damage or old dry grass build-up.

Clean – Old grass on the deck can cause problems. Regular cleaning will prevent build-up and prolong the life of your mower.

Sharpening – A sharp blade will solve lots of cutting and collecting issues.

Wet Grass – It’s much heavier than dry grass obviously, and won’t be thrown as far into the grass bag/box by the laboring engine. It also sticks to the underside of the mower, causing clogging, and preventing the grass catcher from filling. Mowers don’t cut damp/wet grass very well, especially if it’s tall.

Height – How about the cutting height, it may be set too low. I know this sounds obvious but try lifting the deck height, and if you want a tighter cut – drop the deck and cut again. Ideally, your mower shouldn’t be cutting more than an inch of grass, ask it to do more and cut quality suffers.

Try cutting more regularly, keep your mower deck clean and free from dry grass. Consider coating the underside of your deck with Teflon Non-Stick coating, it helps reduce grass clogging.

Tallgrass – Tallgrass is hard on a mower, especially if you’re asking it to cut the lawn tight with just one cut. Tallgrass will cause the mower to clog.

To help prevent clogging:

  • Option 1 – Quick fix is spray the deck with WD40, it does help but it won’t last.
  • Option 2 – Spray deck with DuPont Teflon coating.
  • Option 3 – Spray the the deck with bed liner, my preferred option. Works on tractors, riders and walk behind mowers.

What Is Mulching?

As you know mulching blades chop grass very finely and drop it back onto the lawn where it helps feed the lawn. Mulching blades are designed specifically for this task, but they can cause lots of clogging problems, especially if the grass is long or damp.

Mulching blades just don’t move grass efficiently, because they’re not designed to. They work best when the grass is cut dry, regularly, and in small amounts.

Mulching Blades aren’t designed to collect.

Mulching tall wet grass won’t work, the blade is designed to cut just small amounts of grass at a time.

Hybrid Mulching Blade

As you know a true mulching mower doesn’t collect, its function is to finely chop and drop the clippings. This type of cutting is convenient, it’s a lot less work than emptying a grass bag, which gave mower manufacturers an idea.

The Hybrid Blade (3 in 1) – a mower blade that does it all, collects, mulches and discharges. Well, it does an OK job, but if conditions become challenging the quality does suffer, especially if conditions are wet.

The complaint I hear most with the 3 in 1 mulching blades – won’t fill the grass catcher. The solution – remove the mulching blade and fit a lift blade.

If you don’t want to mulch, change your blade for a lift blade, you will eliminate lots of clogging, clumping, and half-filled grass bags.

3 in 1 – The Hybrid mulching blade, kind of ok at everything.

Lift blade is also known as the 2 in 1, so-called because it bags and discharges. The lift blade vacuums the grass upright, before cutting and moving clippings to the bag.

They’re designed for collecting grass and are available in low, medium, and high lift. A higher lift blade will require a more powerful engine. The lift is created by curving upwards of the trailing edge of the blade. The higher the lift the better the bagging. If you love bagging – You need a lift blade.

Honda 3 in 1 – The Honda Hybrid mulching blade is the best in the business, unfortunately, it can’t be fitted to other mower makes. The reason the Honda is so good at mulching and collecting – twin cut blade set up. Twin stacked blades working together allow blades mulches and move the clippings. Smart!

Grass Bag Won’t Fill

A grass bag/box that doesn’t fill, has a few likely causes. The obvious ones: clogged chute; thatched grass bag; damaged or worn blade; insufficient throttle; poor engine performance.

Thatched – A thatched grass bag is a common problem. Mowers often get cleaned at the end of the season (well some do) but bags rarely do. Examine your bag/box, as a guide, when held to the light you should be able to see through it. If the air can’t pass through the bag, then grass won’t be carried into the bag.

A stiff brush will remove the old thatched grass or better, use a power washer. Cleaning – Stiff brush or a power washer does the job.

Chute Clogs – A clogged chute can be a symptom of an underlying problem. So clearing the chute may not resolve the issue. Check the chute for damage or old dry grass build-up. Grass build-up or damage to the underside of the deck can cause the grass to catch and clog.

Deck Coating – The underside of the deck should be smooth so that the grass moves freely around the deck, up the chute, and into the bag. DuPont makes a Teflon Non-Stick coating which helps reduce grass clogging.

Check out the deck coating video here.

Cleaning – Move your mower to a suitable location as it leaves a bit of a mess. Just attach and turn on the garden hose. Start your mower to engage blades.

Why The Grass Trailing’s?

Grass trailings are commonly caused by a poor fitting or damaged grass catcher. If you find your grass catcher is damaged, consider buying a new one, they’re available to purchase with or without the metal frame.

Check if the bag/box sits correctly against the mower body. If it’s loose or damaged, the air and grass flow to the bag is compromised.

If all is well with the grass catcher, go ahead and replace your blade.‚Äč

Trailings are really annoying, check the bagger is closing snugly.

Check For Blade Damage – A defective blade can cause vibration, uneven cutting, and poor grass collection. Examine your blade, checking for damage, misalignment, bent or broken trailing/leading edges.

Sharpening

Blades need to be kept sharp. I recommend about twice per season or more depending on terrain. Obviously, if your blade is dull it can cause all sorts of problems, including blocked chute and grass catcher issues. Check out blade maintenance tools here, they make the sharpening process a ton easier. 

And if you need a video on the process, it covers it here, sharpening blade on and off the mower.

Impact – When blades hit something hard, well, you know! The damage causes vibration and all sorts of cutting issues.

Bent – Bent blades can’t be repaired, just go ahead and replace them.

What Is PTO Slip?

The blade clutch or PTO (Power take-off) won’t be fitted to all lawn tractors, but it’s easy to locate, it lives right under the engine. A clutch system isn’t common on walk-behind mowers but Honda and Toro offer them on the higher-end models.

It may be manual or electric, either way, its job is to lock the engine crankshaft to the blade deck pulley, when you engage the blades on a button or lever. The clutch like a clutch in a car will wear out, and when it does it causes the connection between engine and deck to slip.

Symptoms include poor grass collection, uncut grass, and sometimes a burning smell.

PTO – Check the PTO system. The manual version is engaged by a cable. It lives on the crankshaft, right under the engine. Check that the cable is pulling the PTO lever all the way.

Fitting – Replacing the PTO isn’t difficult, but air tools would make it really easy.

Check Deck Belt Condition

Belt wear is also a common reason for a chute to clog, check the deck cutting belt for damage and general wear & tear. A new belt will transfer more of the engine power to the cutting blades and will improve the cutting and bag filling performance.

Belt types and lengths will be specific. Some brands will only work well using OEM (Original Equipment Manufacturer) belts, check out “Mower belt replacement”.

If you need walk-behind or ride-on mower blades, bearings, sharpening tools, etc. check out the Amazon.com link below.

Amazon Lawn Mower BladesOpens in a new tab.

Worn – A cutting deck belt that’s slipping will be less efficient at collecting.

Check the belt for proper tension, cracking, glazing or contamination.

Damaged – Damaged belts will cause vibration and poor general performance.

A typical deck belt might last 4 – 5 years.

Check Engine Performance

It’s also worth considering, is the throttle set correctly? It should be set to fast/run when cutting. Is the engine running as it should? If the engine power is reduced the mower may still cut well but will be less efficient at collecting.

A small engine tractor or walk behind mower should have a tune-up at the beginning of every season, regardless of how well it might be running.

Belt types and lengths will be specific. Some brands will only work well using OEM (Original Equipment Manufacturer) belts, check out “Mower belt replacement”.

Check out:

“Lawn tractor tune-up”

“Lawn mower tune-up”

Bad Gas

Old fuel is the number one cause of poor engine performance, use a gas stabilizer over the winter to help protect your lawn mower carburetor, check out “Carburetor troubleshooting”.

Tune-up – Mowers like a tune-up at least once per season.

Related Questions

How does grass catcher work? A grass catcher works by collecting the grass that is thrown into the bag by the force of the mower blade wings. The grass catcher works best when the walls of the bag/box are clear so that the forced air from the blade can pass through it quickly.