01. Grass Too Tall/Wet

02. Deck Too Low

03. Dull/Damaged Blade

04. Deck Grass Build-up

05. Throttle Too Low

06. Moving Too Fast

07. Poor Engine Performance 

08. Damage To Deck

09. Deck Belt Slip (Tractor) 

10. PTO Slip (Tractor)

11. Wrong Blade 

12. Grass Bag Matted

The most common problem is clogging and the cause - poor cutting conditions followed by a worn blade. 

Stopping every 5 minutes to clear the underside of the mower isn't much fun! Lawn mower and tractor mower grass catcher troubleshooting is straight forward.

Common problems include: Clumping; Clogging; Uncut grass; Grass bag won't fill.

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. 

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 filling. Bottom line, mowers don't cut damp/wet grass very well, especially if it's tall.

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 should'nt be cutting more than an inch of grass, ask it to do more and cut quality suffers.

My best advice, cut 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.

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.

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 challanging 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.

Lift blade also known as the 2 in 1, so called because it baggs and discharges. The lift blade vacuums the grass up right, 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 the curving upwards of the trailing edge of the blade. The higher the lift the better the bagging.

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 - One blade mulches and the other moves the clippings. Smart!

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.

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.

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.

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 make a Teflon Non-Stick coating which helps reduce grass clogging.

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.​

• 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.
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• 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. 

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 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.

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". 

Its 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.

Check out:

"Lawn tractor tune-up"

"Lawn mower tune-up"

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".