My Lawn Mower
Chute Clogs

Just so FRUSTRATING!! Cutting tall heavy grass, especially if it's wet, will keep you busy clearing the chute all day.

 

So what's going on, why does my mower chute clogs? The most common reason it clogs is because the grass is too heavy, but there are lots of other reasons:

 

  • Poor Cutting Conditions
  • Deck Too Low
  • Dull/Damaged Blade
  • Deck Grass Build-up
  • Throttle Too Low
  • Poor Engine Performance 
  • Damage To Deck
  • Deck Belt Slip (Tractor)  
  • PTO Slip (Tractor)
  • Using Mulching Blade

Lawn mower grass catcher troubleshooting is straight forward, most are common problems and easy to solve. In this guide we'll look at all the most common causes.

 

Grass height, weather conditions and a worn blade will be the most obvious reasons for the tractor or walk behind mower clogging.

 

Conditions & Chute Clogging

As a guide, you should cut no more than 1/3 off a blade of grass at once. For best results a mower shouldn't be cutting more than an inch of grass, and the best lawn height is about 3". Cutting reguarly keeps the workload on the machine to a minimum and it's easier on your lawn.

 

Weather makes a big differance, obviously if the grass is damp the mower is going to struggle to perform. But I understand, sometimes it's nessaccery to cut wet grass when you need to get the job done.

 

A clogged chute can of course be a symptom of an underlying problem. So clearing the chute may not resolve the issue.

 

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. 

 

 

 

Chute


mower grass chute

Clearing the chute may not solve the problem. Check the chute for damage or old dry grass build up.

Clean


mower deck

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

mower chute

Chute

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.


mower deck

Deck Wash Port

Clean the underside of the deck at the end of the season, as the acid in the grass eats away at the metal over the winter.

 

Most mowers will have a garden hose connection on the deck, simply connect your hose and run your blades to clean the underside of the deck. This does a reasonable job at cleaning.

 

 

 

 

Clean


mower deck

The was out port isn't fitted to all mowers. It does a pretty good job of cleaning the underside of the deck.

Hose


mower deck

Move your mower to a suitable location as it leaves a bit of a mess.

Just attach and turn on garden hose. Start your mower to engage blades.

Run until water runs clear - simple!

mower wash port

Clean

The was out port isn't fitted to all mowers.

It does a pretty good job of cleaning the underside of the deck.

Hose

Move your mower to a suitable location as it leaves a bit of a mess.

Just attach and turn on garden hose. Start your mower to engage blades.

Run until water runs clear - simple!


Battery Connections

Deck Coating

After cleaning the deck and allowing it dry thoroughly, spray on a coat of WD40, it'll help protect the deck over the winter and also help keep the deck grass free in the spring.

 

 

Better than that is applying a non-stick film, it works pretty good and it's easy to apply. The best in the business - DuPont Teflon non-stick dry film, and you check out the price on Amazon.

 

 

 

 

mower deck clean

Clean

Lift the front of your tractor, secure it well before climbing under.

A wire brush and paint scraper does the job.

Protect

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 deck with bed liner, my prefared option. Works on tractors, riders and walk behind mowers.


Mower deck Mower deck

Clean


mower grass chute

Lift the front of your tractor, secure it well before climbing under.

A wire brush and paint scraper does the job.

Protect


mower deck mower deck

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 Dupoint Teflon coating.

Option 3 - Spray the deck with bed liner, my prefared option. Works on tractors, riders and walk behind mowers.

Check Your Grassbag

A clogged grass bag is a common problem. Tractors and walk behind mowers often get cleaned at the end of the season (well some do) but bags rarely do. Symptoms of a clogged bag are not collecting or only a half filled grass bag.

 

Examine your bag/box, when held to the light you should be able to see through it. A stiff brush will remove the old grass or use a power washer.

 

Consider buying a new grass bag if damaged. They are available to purchase usually with or without the frame. Check if the bag/box sits correctly against the mower body. If it's loose, the air and grass flow to the bag will leak.

 

 

Bag


grassbag

Thatched grass on the inside of the bag is a common issue.

It prevents air flow through the bag which in turn prevents grass from entering the bag.

Clean


riding mower battery test

As a rough guide you should be able to see through the bag.

A stiff brush or better a pressure washer does a great job.

mower grass bag

Bag

Thatched grass on the inside of the bag is a common issue.

It prevents air flow through the bag which in turn prevents grass from entering the bag.

Clean

As a rough guide you should be able to see through the bag.

A stiff brush or better a pressure washer does a great job.


Ride-on mower battery test

Check For Blade Damage

Two types of blades are common, the lift blade and mulching blade. They are fitted to tractors, ride-ons and walk behind mowers. A defective blade can cause vibration, uneven cutting and poor grass collection.

 

No need to tell you a bent blade is dangerous and should never be repaired. A new blade, bolt and washer is the way to go. 

 

 

Examine your blades checking for damage, misalignment, bent or broken tips. Your blade is the business end of the mower and needs to be in top condition.

 

 

 

Timed Blades

Some deck set ups will have an overlapping cut, although more common on lawn tractors than walk behind mowers. Toro timemaster walkbehind mower has a timed blade set up.

 

To achieve this the blades must be fixed at a set angle in relation to each other. This is done by using a toothed timed belt. If one of the blades hits an object, the blades can go out of time or the belt can break.

 

This leaves the blades free to hit and damage each other, blade damage is common on timed decks. I wrote this detailed guide including pictures to help you replace your " Timed deck belt ".

 

 

Worn Blade

A worn blade will cause clogging, as the carefully engineered blade wears, the trailing edge is less efficient at moving the clippings. The leading edge will also be worn from grit and debris, and sharpening sessions will likely have changed its shape.

 

The average mower should get a new blade every 2nd or 3rd season.

 

 

 

 

 

Ride-on mower engine Ride-on mower engine Ride-on mower engine

Damaged

Defective blades can cause vibration, uneven cutting and poor grass collection.

Examine your blades carefully, checking for damage, misalignment, bent or broken leading and trailing edges.

A mowing blade may look OK, but they do wear.

Mowing blades are engineered to cut and move grass, as they wear they become much less efficient.

A worn blade will cause clogging.

Damage


mower blade mower blade mower blade

Defective blades can cause vibration, uneven cutting and poor grass collection.

Examine your blades carefully, checking for damage, misalignment, bent or broken leading and trailing edges.

A mowing blade may look OK, but they do wear.

Mowing blades are  engineered to cut and move grass, as they wear they become much less efficient.

A worn blade will cause clogging.

Lift Blade

The Lift blade also known as the 2 in 1, so called because it baggs and discharges. Lift blades vacuum the grass up right, before cutting and moving the clippings to the bag. Lift blades are specially designed for collecting grass and come in low, medium and high lift.

 

Lift meaning sucking power, 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.

 

 

 

 

2 in 1

If you like bagging - You need a lift blade.


mower blades

2 in 1


mower blade

If you like bagging - You need a lift blade.

Mulching Blade

A true Mulching blade is designed to cut grass, circulate it around the deck cutting it several more times and dropping it back onto lawn as fine clippings.

 

Youll know a mulching blade when you see it, the leading edge isn't straight, it curves up and down. This causes the grass blades to be cut several times at differant heights -  resulting in fine clippings.

 

A true Mulching blade is not designed to collect.

 

That got engineers thinking - Meet the hybrid mulching blade or 3 in 1. It attempts to do it all, mulch, baggs, discharges, however we all know it can't be excelant at everything, and it isn't.

 

My advice, if your not interested in mulching then fit a lift blade. It will always bag better than any hybrid mulching blade.

 

 

 

 

 

 

3 in 1

Mulching has become quite popular, and manufacturers have responded by making a blade that try's to do it all, but doesn't quite succeed.


mower starter solenoid

3 in 1


riding mower engine

Mulching has become quite popular, and manufacturers have responded by making a blade that try's to do it all, but doesn't quite succeed.

Engine Performance Problems

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.

 

I wrote these guides to help you tune-up your own mower, it includes oil grade chart and quantity for your engine, check out:

 

 

 

"Lawn tractor tune-up"

"Lawn mower tune-up"

 

 

 

 

 

Bad Gas

Stale gas is the number one most common cause of poor engine performance. It's caused usually by letting gas sit in the mower over the winter. The bad gas can damage the carburetor causing 100$$ in repairs and it's not covered by your warranty.

 

This problem can be avoided by using a gas stabilizer, you won't have to use it all season, just at the tail end. It's simple to use, just dump the bottle of gas stabilizer into your gas tank and run the engine to mix it throughout the fuel system, that's it. Your fuel system is now protected against bad gas. Check out the price of Sta-bil gas on Amazon.

 

The fix - remove and clean the carburetor, if it's badly corroded, you'll need to replace it.

 

I wrote these easy to follow guides including pictures on carburteor cleaning, it will help you find your problem and fix it fast.

 

"Lawn mower carburetor cleaning"

"Lawn tractor carburetor cleaning" 

 

 

Tune-up


mower

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

tractor mower

Tune-up

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

What Is Power Take Off (PTO)?

The PTO clutch assembly will not be fitted to all mowers, and so this may not be applicable. It's fitted mostly to tractors, ride-ons and larger walk behind mowers.

 

The PTO clutch is a unit fitted to the end of the crankshaft.The deck belt wraps around the PTO pulley, its function is to apply the power of the engine to the blades when a switch or lever is operated.  

 

 

 

 

 

 

PTO Wear

SThe PTO clutch when worn, will slip reducing power to the blades. This will be especially noticeable in taller grass. The PTO if fitted will be manual or electromagnetic.

 

If manual it will likely have a lever and cable to operate - check that the cable is pulling the PTO. Both types can't be repaired, they must be replaced.

 

 

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.


Ride-on PTO
mower PTO

Fitting

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

PTO


MOWER PTO Riding mower 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.

Tractor Belt Wear Problems

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. 

 

 

 

 

 

 

Cutting Belt 


MOWER PTO Riding mower belt

A cutting deck belt that's slipping will be less efficient at collecting.

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

Damaged belts will cause vibration and poor general performance. A typical deck belt might last 3 - 4 years.

mower deck belt

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 3 - 4 years.


Mower deck belt

Related Questions

Why is my lawn mower spitting out grass? Common reasons for grass trailing is grassbag or box not sitting on the mower deck correctly. Check for gaps around the bag / deck interface and holes in the bag.

 

Grass not going into the lawn mower bag? When your mower isn't filling the grass bag, first try cleaning the bag, if that doesn't help, replace the cutting blade.

 

Auto Technician and Writer at | Website

John Cunningham is an Automotive Technician and writer on Lawnmowerfixed.com. I've been a mechanic for over twenty years, I use my knowledge and experience to write "How to" articles that help fellow gear-heads with all aspects of mechanical repairs, from lawn mowers to classic cars.