I did some checking today and I found that your unit is a 2018 model. Did you purchase it in 2018 or 2019? This unit should have the update spring hardware. Second, you said that this unit is primarily used by you wife, would you ask her, “At what speed does she engage the deck? Third, does the spring break while she is cutting or when the blade is first engaged?
Kubota Z421 Broken Deck Springs
- Thread starter Greaser
- Start date
Rivet we purchased the mower May 2018. She said she engaged the blade while sitting still, the spring breaks while mowing. Thanks for checking. I don’t have a clue, neither does my dealer - they have been great about working with me. It’s Kubota that’s dragging their feet, a Kubota rep told my dealer that he, the rep, would contact me since last Wednesday today is Monday - still no contact. I found out that the lemon law does not apply in Tennessee, however since I had to purchase another mower I do have other options.
Sorry, by speed I meant engine speed. In talking to our dealership owner, been working on Kubotas for 50+ years, he says that these units need to have the deck engaged at nearly full RPM’s. Because of the very tight belt tension, engaging at lower speeds causes excessive slapping of the tensioner arm, pulley and spring. The weakest one is the spring, which eventually breaks. Does the spring break at one of the connecting curls? That’s where the spring will bang back and forth losing contact and hammering. This may be the cause of your problem. That was the main reason for the updates on the older units, didn’t have strong enough tensioner arm, pulley and spring. I’ll bet the rep doesn’t even know this.
I would attach a picture of the broken spring, but I can’t figure out how to do an attachment. But the spring breaks about 3/4 inch from the spring windings. About the speed, I’m guessing about half throttle - I know she doesn’t have the RPMs wound up. Thanks, I’m interested in what the rep says as well - although I’m more interested when he will make contact.
Chris32
Forum Newbie
- Joined
- Jun 14, 2020
- Threads
- 0
- Messages
- 1
I have a Kubota Z421 that has broken 2 tension springs on the drive belt recently. One at 33 hours and another at 39 hours. This spring is obviously made cheap, or they have a design flaw. Both have broken about an hour into cutting and the blades are in high speed. It's very frustrating and ruins my entire opinion on Kubota mowers. Picture attached.
