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I’m having an issue with 40hrs on my lawn mower. The spring has broken 3 times and the service department continues to tell me it’s due to a small piece of a pinecone or stick. I’m so tired of having to go up there every single time this breaks. It’s ridiculous. I had a cub cadet from Home Depot for 9 years with no issue and cut over rocks, roots, and hill sides. Now I live where I have a flat yard sod and some pines and cannot keep this lawn mower running.

So the spring on the deck that tensions the belt? Something doesn't seem right for sure. Does it happen while mowing or when engaging the blades?

How many springs does that mower have that could break?

Darryl G said:

So the spring on the deck that tensions the belt? Something doesn't seem right for sure. Does it happen while mowing or when engaging the blades?

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It’s the spring on the drive pully. It hooks to a pully and a bolt. It will break wether the blades are engaged or not. Talladega tractor replaced it the first time and then I replaced it the second and they replaced it the third. I lifted the lawn mower up and checked all the pullys to make sure there was nothing in the pullys and they were all in line and moving properly before I took it back to them. When I took it back they said a pine comb was stuck in one of the pullys. Which was a complete lie. So idk why it keeps breaking.

Here is pic of spring

typical foreign trash. locate a different dealer if possible and contact HQ if possible.

OEM spring may be just a little lacking for the application or just a bad batch of springs from the vendor. I would find a spring at the hardware or farm supply store that is similar and see what happens. I replace springs that break on old mowers where parts are NLA all the time with hardware store ones. The stick in the pulley or belt seems to be a standard line.

SeniorCitizen said:

typical foreign trash. locate a different dealer if possible and contact HQ if possible.

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Thank you!!!!! Will do

Hammermechanicman said:

OEM spring may be just a little lacking for the application or just a bad batch of springs from the vendor. I would find a spring at the hardware or farm supply store that is similar and see what happens. I replace springs that break on old mowers where parts are NLA all the time with hardware store ones. The stick in the pulley or belt seems to be a standard line.

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Good thought, I’m scared that since it only has 40hrs and I use something different, it may void my warranty.

SeniorCitizen said:

How many springs does that mower have that could break?

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At least 2...

Have a few questions to ask. 1. Has your dealer installed the update kit on your deck? There is one available under warranty. 2. Can you remove the belt covers and post a few pics of the deck? I would like to see if you have the proper spring dampeners installed. Close ups would be the best. 3. Does the tensioner arm move freely? Please post the model and serial numbers off the black ID tag. In my opinion your dealer is giving you a line when talking about pine cones. Most often the belt will break before the springs. If we find you need the update kit, I would find another dealer, as you have a good unit but a lazy dealer.

the spring in the picture is the updated spring.

The #1 cause of spring failure is excessive vibration. That can be caused by a lot of things; most commonly a small piece of debris in the engine pulley, which causes the belt to jump, which makes the spring vibrate. Running at idle speed will also break the spring, as will a burned belt and a host of other things.

There was a campaign (like a recall) that did 4 or 5 repairs, but that campaign expired. It was 2 years long and letters were sent. Only certain serial numbers were affected. At this point the recommendation to the technicians doing the warranty repair is to visibly inspect each of the 5 pulleys for debris, then measure the belt width in many locations along the length of the belt. If those check out, they're going to want to look into pulley alignment too. This is assuming you're running full throttle wide open all the time, and the reason I mention it is because at idle speed the pulley and spring jump around quite a bit more than they do at 3500 engine RPM.

The only updated spring comes in a kit and the entire kit, pulleys, tensioner arm, belt and spring should be installed. They need to even drill new holes in the deck for the new tensioner arm. If I was you. I would take the model and serial numbers for your unit to another dealer and ask them to check Kubota records to see if this was done. There is no time limit on this update, as the dealers were to contact you when they got the kits in. Took us 18 months to get through our sold units. Second, I don’t know who told you that running at idle speed would cause a spring to break, but I say he’s full of it.

Rivets said:

The only updated spring comes in a kit and the entire kit, pulleys, tensioner arm, belt and spring should be installed. They need to even drill new holes in the deck for the new tensioner arm. If I was you. I would take the model and serial numbers for your unit to another dealer and ask them to check Kubota records to see if this was done. There is no time limit on this update, as the dealers were to contact you when they got the kits in. Took us 18 months to get through our sold units. Second, I don’t know who told you that running at idle speed would cause a spring to break, but I say he’s full of it.

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That update consisted of several updates in one. One was a belt guard kit (48 and 54), one was the updated hst belt spring, then the tension arm kit (48" deck only), a brake switch kit, then finally the fuel pickup tube/shutoff valve assembly. There were serial number breaks; meaning that not every one of them was eligible and some were done at the factory. That set of bulletins (campaign) is now expired; it was active for, gosh, 2 years? I think it came out in early 2018, expired this year. Everyone who purchased a ZG or Z100 series got a letter, if it was purchased used, you probably didn't get a letter, however anytime one was at the dealer it was supposed to be checked to see if it was done or not; if not it was best to go ahead & do it if applicable. As said the spring in the pic is the updated spring. The issue with the OP is debris entry into the engine pulley which the campaign would not have addressed.

Hole does not need to be drilled for the tension arm kit. Holes need to be drilled for the belt guard kit (which is completely separate from the tension arm kit). There is a set of bolt-on pins that are to be installed and there are no holes for the bolts to hold the pins on, 2 holes per, and then a larger hole for the right side 8mm bolt and spacer.

Yes running at or near idle speed can cause the spring to vibrate more than usual, particularly the deck tension spring-which if you pull the covers and look at the belt and tension spring while idling with the deck engaged, you'll see what I mean. The spring disappears because it vibrates so badly.

The Z231 and Z251 have been updated in a few ways and parts of the update may retrofit-I haven't tried yet.

I have a z421-60" , drive spring broke at 80 hrs., mower is going back today, since the spring broke, I've gone thru 4 belts, I now have 155 hrs on it. The current belt that just broke, lasted 5 hrs! Seriously considering selling this mower.

Olracer said:

I have a z421-60" , drive spring broke at 80 hrs., mower is going back today, since the spring broke, I've gone thru 4 belts, I now have 155 hrs on it. The current belt that just broke, lasted 5 hrs! Seriously considering selling this mower.

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Go ask your dealer about the hst belt update kit. They are replacing the hst pulleys among other things, including adding a debris guard to the back of the deck which seems to solve the issue. In addition, the debris guard helps give your lawn a nice set of stripes so long as the deck is leveled properly. I put a few on while I worked at the dealer and on the Z400 series, they're a little more involved--but those that I followed up with, had zero issue out of them after the pulley/guard kit installation. Kubota was taking care of the bill too, but keep in mind I left the dealer in September 2020, so you will want to call them and inquire. Tell them your belt keeps coming off and ask them about a bulletin that addresses this issue. Kubota didn't send any letters to anyone about it, nothing, neither did the dealer. It's a fix-as-fail bulletin meaning they aren't fixing any of them unless the consumer is having a problem keeping belts on, which it sounds like you are. There is also some serial number "breaks"--meaning they aren't fixing ALL of them, only once in certain serial number ranges. Again, you're best to call them.

It is unfortunate that a few of these mowers had this issue. I'm happy that Kubota is (was?) taking care of them at no charge to the customer. They are as passionate about fixing known-issues as any manufacturer that I have been around which is one reason I own a Kubota. I love the Z400 series and at some point may buy one to replace my ZG127S-54.

Chris6197 said:

Good thought, I’m scared that since it only has 40hrs and I use something different, it may void my warranty.

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Keep an old broken spring and a new spring hat has been used 50 hours or so and sllp that on before getting it serviced.
No one knows what was on there when you were mowing but you.

Sounds like a bad batch of springs.
I had a problem with clutch springs on Honda SP breaking.
Had a whinge to the rep and sure enough here was a replacement programme a few months latter and he new spring were just a touch thicker wire.
Problem with differences between metric & imperial wire gauges.