Mower Deck Belt Replacement
Tension-ed or Not
This type belt is always tight on the pulleys.
This type belt setup is slack on the pulleys until you engage the blades.
What Deck Type?
Measuring The Belt
What Belt Width?
What Belt Length?
Sometimes easier said than done!
Check under the hood of your mower, you may get lucky with a part number sticker, but be cautious with the Husqvarna labelling, they are often wrong belt part numbers.
Check your old belt for markings, if none, get a tape and some string.
These belts are measured in mm.
The new belt will be the full width of the pulleys.
Worn belts usually stretch in length and become narrow in the width.
Check Belt Routing
Belt Routing Links
Check under the foot rest of your mower, some models have a belt routing sticker.
This sticker is on a Husqvarna tractor.
This is a common deck fitted to lots of makes.
This type deck has a Mandrel brake, apply the blade engage lever after you have removed the belt from the engine pulley.
This allows you remove the belt.
What Belt Type?
AA Hex Belts
The B type belt is a heavy duty A belt, its older well fed brother.
AA Hex Type
This is a double faced belt, it gives greater flexibility to deck design, as it allows both sides of the belt drive.
It's used on higher end tractor decks.
Check Belt Wear
How Long do they last?
A worn or damaged pulley can shorten the life of your belt. An engine or transmission oil leak can destroy the belt, you can try cleaning it, but it causes slip. A derailing belt can get twisted and damaged, a mower that throws belts regularly, probably has a worn or damaged pulley.
Flat spotting is usually caused when the blade jams but the engine pulley keeps running. This has a grinding effect on the belt.
The flat spot will cause excessive vibration in the mowing deck. The fix - Replace the belt.
This can happen when a belt gets old, the material is starting to break down.
Your mower won't cut or collect very well. Better to take care of it now, before it breaks.
This belt has a shiny hard surface, not much good for traction.
A belt like this will cause horrible vibration in the mowing deck.
Wear and tear, this belt is at the end of its useful life.
Check Pulley Wear
This is a V pulley, the driving side of the belt is making contact with the pulley.
Spin To Test
Fitting A Belt
On this model mower the chute is fitted through the center of the mower.
Not all mowers will have a chute like this. If your mower is side discharge, then you don't have one.
As said earlier, you may not need to remove your deck to fit a belt.
On this model mower, removing to fit the belt just makes life a little easier.
When all pins are removed, just push the deck sideways and it will pop off the arm bushing mounts.
Apply some grease when refitting.
The deck will be free to move forward, which allows you to remove the deck drive belt from the engine drive pulley.
In some cases you may have a cable to remove, this depends on the blade engage type.
Remove the deck drive belt from the engine drive pulley, as you slide the deck forward.
Or if your leaving the deck on the mower, just pull the belt over the side of the pulley and turn over the engine (by hand) by turning the pulley, (spark plug removed) until the belt falls off.
Hey, I make that sound easy!
If your blades are bent or worn, now is the time to take care of it.
Replacement blades are easy to fit, when the deck is off.
Remove plastic protection covers.
Remove the drive belt tension assembly.
Remove and store safely the key and the spacer ring.
Remove timed belt protective cover.
Remove broken belt, and check for damage.
Remove the two guide bolts.
Remember to fit these after fitting the belt, but tighten last.
Loosen the two guide bolts.
Loosen the lock-nut on the adjusting bolt, and thread it all the way out.
Now push the tensioning assembly in all the way so it hits the adjusting bolt.
Set to 90°
Set the deck blades at 90° to each other.
Now mark the two main blade pulleys and the deck body as per picture.
Marking them with paint gives us a clear reference point when fitting the new belt.
This is a typical timed belt routing.
Check your paint marks again, it's OK if your out by one or two teeth.
Adjust belt tension first, and tighten down lock-nut.
Do not tighten pulley bolts or guide bolts at this stage.
Check that the blades are at 90 degrees.
If all is OK, go ahead and fit the guide bolts, but don't tighten yet.
Tighten the two pulley bolts, and now tighten the four guides.
Rebuild in reverse order and don't forget to fit the spacer ring and key.
That wasn't so bad!
- Wrong belt routing
- Misaligned pulley
- Damaged pulley
- Belt guide missing
- Belt guide damaged
- Belt too loose
- Belt too tight
- Belt too narrow
- Wrong belt type
- Blade obstruction
- Engine not at the correct rpm
- Engine not running correctly
- Blades damaged
- Deck belt damaged or worn
- Spindle bearing damaged or broken