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Mower deck problem diagnosis

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Mower deck problem diagnosis

Postby AJB Temple » 17 Jun 2022, 13:55

I have a Stiga Park ride on centrally articulated mower with zero radius turn and forward mounted electrically adjustable 120cm cutting width deck.

The deck has started to make a lot of noise lately, basically an "I'm about to fall apart soon" shout. The machine is 5 years old and well maintained except I don't thing the deck bearings have ever been greased (can't see how). I am guessing that the racket is caused by the deck bearings being worn. Is this likely?

The system works by a pulley from the engine driving a long belt to the blade deck where there is a similar central pulley. This distributes power (presumably by pulleys and belts as well to the three blades. I can't see these belts without taking the deck off and stripping it, but the main drive belt to the deck is in good nick and not loose.

Any amazing insights from you machinery experts before I start to strip the deck? No rush as it is working, but the noise is worrying me. I do not (yet) have a spider thing to get pulleys off, nor do I have any special bearing tools.
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Re: Mower deck problem diagnosis

Postby Lurker » 17 Jun 2022, 14:20

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Re: Mower deck problem diagnosis

Postby Trevanion » 17 Jun 2022, 15:33

I'd be surprised if it was knackered bearings on a ~5-year-old machine, but then again it isn't the most polite environment for mechanical parts especially if there's no way to service them (greased for life bearings). They would have to be practically destroyed for you to hear them making noise above the noise of the motor though.

Did you try jiggling the blades by hand to see if they have lateral movement or rattle? That would be the first sign of a bearing that's worn out, or that the blade is loose.

My main concern if there's a lot of noise would be if there's a pulley working loose.
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Re: Mower deck problem diagnosis

Postby AJB Temple » 17 Jun 2022, 15:50

The engine, since I serviced it is quite quiet 8-)

I have the deck up quite often to clean the underside and touch up the cutting edges, and there is no lateral movement in the blade shafts as far as I can tell. The noise is like a very loud rattle, but there is no excessive vibration from the deck and it is cutting cleanly. I haven't had the blades off for balancing for quite a while but I doubt that is an issue.

I am wondering if I have done something stupid with the belt runs.

The machine is not heavily used as it is just a home mower and there is about an acre of grass. Typically an hour a week through the season (say March to November) - say 40 hours a year.
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Re: Mower deck problem diagnosis

Postby eezageeza » 19 Jun 2022, 08:47

Could something have got into the area where the drive belt / pulleys interact ? Garden detritus of some sort making a racket ?

My last cutter deck rusted through after about 15 years, and the bearings were still going strong, so I think it probably isn't worn bearings you're hearing, although you might just be unlucky and have a duffer!
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Re: Mower deck problem diagnosis

Postby clogs » 19 Jun 2022, 19:35

your lucky they have lasted that long really....
even with decent replacement bearings 2-3 years is about it before they get grumbly....
I used to repair them for a living......
now most repair shops will just replace the tower.....loads'a money....
But it's not a big job to change the bearings....top n bottom....
drop the tray...pls photgraph the belt run...it's easy to get it wrong....
pop off the nut where the top pulley is, remove the pulley then with a peice of plastic or hard wood
knock the shaft downwards.....it wont take much....u dont even have to remove the blade.....
then the whole shaft and bottom bearing will drop out.....
often the bot bearing is a lot larger than the top one...so just falls out....
simply tap off the bearings if they havent fallen apart and replace with
QUALITY bearing, not the Chinese cheapo's.....if u have the option use the double rubber sealed bearings not the metal sealed ones....they both are lubed for life.....
and rfit in reverse order...
I used simply bearings or others.....their on line cattalog will have the same brg numbers and the option of the double sealed variety...prob about £5-8 a pair.....
I used to buy bearing by the 20....they went that often....
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Re: Mower deck problem diagnosis

Postby AJB Temple » 19 Jun 2022, 20:21

Thanks. Very helpful.

The deck is well maintained and not rusty as I lift it regularly to clean the grass out and sharpen the blades. Probably 4 times a year. It's not dead easy as you have to drop the deck linkages off the axles and release the deck top cover to free the belt.

Zero rust as I repaint the underside each winter and grease all the lift points regularly. I have already discovered that the local repair shops are shysters (the guy I bought the mower from is decent, but he sold up and retired).

I think I will whip the deck top off and replace the belt with a new one anyway. I can't take photos as I don't have a lift, and when you tip it up the belt run is disturbed a lot.

The belt side guard underneath the engine (ie mower side not deck side) was damaged when offspring replaced the belt a while ago and ran the belt incorrectly through the guides. Burnt out the guard and belt. But I fixed that and it was fine. I do know that the machine is belt sensitive and I have a new blue heavy duty one in stock.

I checked the gauge today (which I was unaware was there) and the mower has done 320 hours of total use since new. Some of this is just towing a trailer around (so deck disengaged), mostly up and down to the workshop. 320 hours seems trivial to me for bearings. I would think the only way that the bearings are knackered ought to be if the belt tension on the shafts is too much? 320 hours of total use, with maybe 5% deck not running, equates to under 40 working days of use in total.
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