Mower Part Warranties Explained — Why Rotary & Stens Beat Most OEM Guarantees
Most OEM parts carry only a 90-day warranty. Rotary and Stens both warrant their parts for a full year. But there’s a labor reimbursement difference that dealers rarely explain — and it changes the calculation.
When most people think about warranty coverage on mower parts, they assume OEM wins by default. The brand name is on the box, the manufacturer stands behind it, and it must carry the best protection available. The reality is more nuanced — and in one important respect, significantly different from what most equipment owners expect. Many OEM replacement parts carry only a 90-day warranty against defects. Two of the largest aftermarket parts suppliers in the outdoor power equipment industry — Rotary Corporation and Stens — both warrant their parts for a full year on most products. That’s four times the coverage period of many OEM parts, and it’s a detail worth understanding before you make your next parts decision.
But warranty coverage isn’t just about duration. There’s a second distinction — one that matters enormously if a part actually fails — that dealers understand but rarely spell out for customers. It involves who pays for the labor when a defective part needs to be replaced. That difference can turn a straightforward warranty claim into an unexpected bill, and knowing about it in advance is the kind of information that protects both your equipment and your wallet.
OEM Warranty Coverage — What It Actually Covers
When you purchase an OEM replacement part through an authorized dealer and that part fails due to a manufacturing defect, most OEM manufacturers will cover both the cost of the replacement part and the labor required to install it — provided the part was installed by an authorized dealer and the failure occurred within the warranty period.
That labor coverage is significant. A warranty claim on a defective starter motor, for example, isn’t just about the cost of the part. By the time a technician diagnoses the issue, removes the failed component, installs the replacement, and tests the repair, you’re looking at one to two hours of shop labor. At current dealer labor rates — typically $85 to $120 per hour — that’s $85 to $240 in labor charges on top of the part itself.
Under OEM warranty with dealer installation, that labor is reimbursed by the manufacturer. The dealer files the claim, the OEM pays, and the customer walks out without a labor bill. That’s a genuine benefit of buying OEM parts and having them installed at an authorized service center.
“When an OEM part fails under warranty and was dealer-installed, the manufacturer typically covers both the part and the labor. With aftermarket, the supplier covers the part — the labor cost falls on you or your dealer.”
From the Parts CounterAftermarket Warranty Coverage — The Important Difference
Both Rotary Corporation and Stens — two of the most established names in aftermarket outdoor power equipment parts — offer a limited one-year warranty to the original purchaser covering defects in material and workmanship under normal use and service on most of their products. That’s a longer coverage period than most OEM parts warranties — and it covers repair or replacement of defective parts, including items damaged by a defective product from either supplier.
The key distinction is what it doesn’t cover: labor. If a Rotary part fails due to a manufacturing defect within that one-year window, Rotary will replace the defective part. The cost of having a technician remove the failed part and install the replacement — that’s the purchaser’s responsibility. Shipping costs for returning a defective part are also the purchaser’s responsibility, and warranty claims are handled through authorized Rotary service dealers.
- Duration: 90 days from purchase (most parts)
- Covers: Defective parts and materials
- Labor: Reimbursed when installed by authorized dealer
- Shipping: Typically covered by manufacturer
- Claims: Through authorized OEM dealer
- Requirement: Dealer installation for labor coverage
- Duration: One full year from purchase (most products)
- Covers: Defective parts, including items damaged by defective product
- Labor: Not covered — purchaser’s responsibility
- Shipping: Purchaser covers return shipping
- Claims: Through authorized service dealers
- Requirement: Normal use and service conditions
What’s Not Covered — by Anyone
Understanding what voids a warranty claim is just as important as knowing what’s covered. Both OEM and aftermarket warranties exclude normal wear, routine maintenance, and failures caused by factors outside the part itself. This is where a lot of frustration at the parts counter comes from — customers expecting a warranty claim on a failure that was never a warranty issue to begin with.
These situations are not covered under any parts warranty, regardless of brand:
- A branch or debris gets caught in the deck and snaps a belt — that’s impact damage, not a manufacturing defect
- A belt keeps breaking repeatedly — but the real cause is an idler pulley with a failing bearing, or a nicked pulley groove damaging the belt on every revolution
- Normal wear on blades, belts, filters, and other consumable items that have reached end of service life
- Damage caused by improper installation, incorrect part selection, or operation outside manufacturer specifications
- Corrosion, rust, or deterioration from storage or environmental conditions
The belt example deserves special attention. Repeated belt failures are one of the most common warranty disputes at the parts counter — and almost always, the belt is fine. The problem is an underlying mechanical issue: a bearing going out in an idler pulley, a pulley that’s developed a nick or groove from debris impact, a misaligned spindle, or a worn tensioner. Replacing the belt without diagnosing the root cause means the new belt will fail too, and no warranty will cover that.
Real-World Examples — How This Plays Out at the Dealer
A customer’s zero turn won’t start. The dealer diagnoses a defective OEM starter motor — it’s a manufacturing defect that showed up at 45 days. The part is under the OEM 90-day warranty and was installed by the authorized dealer.
The OEM replaces the starter at no charge and reimburses the dealer for the labor to diagnose and install the replacement. The customer pays nothing. This is the OEM warranty working exactly as intended — and it’s a genuine benefit of buying OEM through an authorized service center.
A customer installs a Rotary or Stens deck belt themselves and it fails due to a manufacturing defect at four months. The belt is within the one-year warranty period. The supplier replaces the belt at no charge.
However, the customer now needs to install the replacement belt. If they bring it to a dealer, that’s one hour of shop labor — $85 to $120 — that the aftermarket warranty doesn’t cover. The customer absorbs that cost. Whether that matters depends on whether the customer planned to do the install themselves anyway.
A customer comes back with a third broken belt in two months, convinced they received defective parts. After inspection, the real problem is a failing bearing in the idler pulley — every time the belt runs, the rough pulley surface is destroying it within weeks.
No warranty — OEM or aftermarket — covers this situation. The belt isn’t defective; the pulley is the culprit. This is one of the most important diagnostic points a parts professional can share with a customer: before assuming a part failure is a warranty issue, rule out the mechanical conditions that could be causing it.
The Honest Calculation — Which Warranty Is Actually Better?
The answer depends on your situation, and it’s worth being honest about both sides rather than declaring a simple winner.
When OEM Warranty Has a Real Advantage
If you’re having parts installed by an authorized dealer, OEM warranty coverage with labor reimbursement is a meaningful benefit — particularly on higher-cost labor items like starters, electric PTO clutches, and alternators. A defective starter replaced under OEM warranty with dealer installation is a true zero-cost outcome. That’s real value, especially for commercial operators where downtime and shop visits are already expensive.
When Rotary and Stens One-Year Warranties Have a Real Advantage
If you do your own installation, the labor reimbursement distinction disappears entirely. A DIY owner who installs their own filters, belts, and blades gets no benefit from OEM’s labor coverage — and in that case, the one-year coverage offered by Rotary and Stens on the part itself is straightforwardly better than a 90-day OEM warranty. Four times the coverage period, on a part you’re installing yourself, from suppliers with documented track records in the industry.
For commercial operators running their own maintenance programs, the same logic applies. An in-house technician doing routine maintenance isn’t going to file an OEM warranty labor claim for a belt — but they will benefit from a longer defect coverage window on the parts they’re buying in volume.
- Most OEM replacement parts carry a 90-day warranty. Rotary and Stens both warrant their parts for a full year on most products — four times longer.
- OEM warranty includes labor reimbursement when parts are installed by an authorized dealer. Aftermarket warranty covers the part only — labor is the purchaser’s responsibility.
- If you use a dealer for installation, OEM’s labor coverage is a genuine benefit worth factoring into your parts decision, especially on higher-labor items.
- If you do your own installation, the one-year part coverage from Rotary or Stens is the better warranty by a significant margin.
- Neither OEM nor aftermarket covers impact damage, wear, or failures caused by underlying mechanical problems. Diagnose the root cause before filing any claim.
- Repeated failures of the same part — belts especially — are almost always a mechanical issue, not a defective part. Check idler pulleys, bearings, and pulley condition first.
- Warranty claims on aftermarket parts go through authorized service dealers for each supplier. Know your dealer before you need a claim.
Frequently Asked Questions
Most OEM replacement parts — starters, belts, filters, blades, and similar components — carry a 90-day warranty against manufacturing defects. Some OEM parts, particularly larger assemblies or electronics, may carry longer coverage, but 90 days is the standard for most replacement parts. Always check the specific warranty terms for the part you’re purchasing.
No. Both Rotary and Stens warrant their parts for one year on most products, covering replacement of defective parts including items damaged by a defective product. Neither covers labor costs associated with removing the failed part or installing the replacement. The purchaser is also responsible for shipping costs when returning a defective part for warranty service.
Generally no. OEM labor reimbursement applies when an authorized dealer performs the installation. If you install an OEM part yourself and it fails under warranty, the manufacturer will typically replace the defective part but will not reimburse labor for a self-install. Labor coverage is specifically tied to dealer-performed work.
Almost certainly not. Repeated belt failures are one of the most common parts counter conversations, and in the vast majority of cases the belt is not defective. The real culprit is usually a failing idler pulley bearing, a nicked or grooved pulley surface from debris impact, a misaligned spindle, or a worn tensioner. No warranty — OEM or aftermarket — covers belt failures caused by underlying mechanical problems. Always diagnose the root cause before replacing the belt again.
Yes — impact damage is not a manufacturing defect. If a branch, rock, or other debris gets caught in the deck and causes a belt to snap, that’s a damage event, not a product failure. Warranties cover defects in material and workmanship under normal use — debris impact falls outside normal use conditions regardless of which brand part you’re running.
Warranty claims on Rotary and Stens products are handled through authorized service dealers for each supplier — not directly through the companies themselves. If you purchased a part through a dealer or parts supplier, contact them first. The purchaser is responsible for shipping costs associated with returning a defective part for warranty evaluation.
Not necessarily — it depends on what the warranty covers and how you use it. A one-year parts-only warranty may be less valuable than a 90-day warranty that includes dealer labor reimbursement, depending on who is doing the installation and what the labor cost would be. Evaluate the full picture: duration, what’s covered, what’s excluded, and whether labor reimbursement applies to your situation.