Husqvarna Lawn Mower Spark Plug by Engine (4 Types, 3 Gaps)

The 50-Word Answer: Which Spark Plug Your Husqvarna Takes

A Husqvarna lawn mower spark plug is set by the engine, not by Husqvarna. Briggs & Stratton Sprint flatheads take a Champion RJ19LM at .030 inch through a 21 mm socket.

Briggs & Stratton OHV and EXi engines take a Champion RC12YC class plug through a 16 mm socket, gapped at .020 inch on current walk-behinds. Honda GCV engines take an NGK BPR5ES or BPR6ES. Kawasaki and Kohler V-twins take two NGK BPR4ES plugs.

Those nine plugs produced four different part numbers and three different gap specs. Not one of them was an NGK BPMR7A, which is the answer most of the internet gives for this exact question.

One brand cannot have one plug here, because Husqvarna buys its US mower engines from four different suppliers. Each supplier sets its own heat range, thread reach and gap, and Briggs & Stratton's own spark plug and gap chart splits the gap again by engine code date.

The box is a route. The engine tag is the answer. Use the table to know what to expect, then confirm it against the label on your engine before you buy.

Read the Engine Tag, Not the Hood Decal

NGK BPMR7A, sold as Husqvarna part 503235111, is not a lawn mower spark plug. Husqvarna's own spare-part catalogue lists that plug under HQT-1 and files it as handheld, and the dealer fitment list runs to chainsaws, string trimmers, brush cutters and cut-off saws with no mower on it.

Husqvarna does not build the engines in its US mowers. Briggs & Stratton, Honda, Kawasaki and Kohler do, and each one specifies its own spark plug.

The plug is real and it is genuinely Husqvarna. The Husqvarna parts listing for 503235111 describes an NGK BPMR7A with an M14 x 1.25 thread, and it is the correct plug for a 435, a 445, a 455 Rancher, a 372 XP and a 223L trimmer.

It is simply from the other half of the catalogue. Search the Messick's fitment listing for the same part number and you get hundreds of handheld models and no walk-behind or riding mower at all.

I put the two plugs side by side on 22 March 2026, a BPMR7A out of a Husqvarna 435 chainsaw and the Champion RJ19LM out of my 2009 Husqvarna 5521P walk-behind. On the caliper the BPMR7A reads a 19 mm hex against the RJ19LM's 21 mm, and its thread reach is visibly shorter.

That reach difference is the part that matters, and Husqvarna's catalogue confirms it in print: HQT-1, the BPMR7A row, carries 9 mm of thread reach against 19 mm for HQT-9, the Champion RC12YC row a Husqvarna rider actually uses. Reach sets how far the electrode sits into the combustion chamber, so a two-stroke saw plug is not a smaller mower plug but a different thermal design.

So the rule is short: the engine tag decides, not the hood decal. If a page names one spark plug for every Husqvarna mower, it has not looked at your engine.

The part is genuine. It is just not for your mower. Anyone who bought a 503235111 for a lawn mower was not sold a fake. They were routed to the wrong product line by pages that treat Husqvarna as an engine brand.

Find Your Husqvarna's Body Style and Engine in 60 Seconds

To find the right spark plug for a Husqvarna lawn mower, read the engine identification label, not the mower model tag. On walk-behind Husqvarnas that label sits on the blower housing beside the recoil starter or on the top of the engine shroud near the muffler.

On lawn tractors and zero-turns it sits on the blower housing or the valve cover under the hood. Briggs & Stratton labels carry a Model, Type and Code. Honda and Kawasaki carry a series code such as GCV160 or FR651V.

Start with body style, because it narrows the field before you open anything. It will not finish the job, though: an LC221A and a 7021R are the same shape and take different plugs at different gaps.

How to Read Your Husqvarna Engine Tag in Four Steps

1. Pull the spark plug boot straight off the plug so the engine cannot start while your hands are near the blade.

2. Find the metal or foil label on the engine itself. On walk-behinds look at the blower housing beside the pull cord; on riders and zero-turns, open the hood and look at the blower housing or the valve cover.

3. Read the whole code. On a Briggs engine you want the Model, the Type and the Code, and the Code is the eleven-digit date string that decides your gap. On a Honda or Kawasaki you want the series, such as GCV160 or FR651V.

4. Match the first characters to a family: Sprint and Quantum are L-head, EXi and Intek are OHV, GCV is Honda, FR and FS are Kawasaki, 7000 Series is Kohler.

That whole pass took me eleven minutes across all six machines, including photographing each label, and the outlier was the Z254, where the Kawasaki FR651V label sits behind the seat pan and needs the seat tipped forward.

The deck decal will not substitute for it: Sears PartsDirect notes for the LC221A that the same model code has shipped with different engine variants, so the decal confirms the mower and nothing else.

Identifying the engine is also the first step in any complete lawn mower tune-up, since the air filter, the oil spec and the plug are all engine-specific rather than Husqvarna-specific.

Label gone? Read the plug you pull. If the tag is corroded, painted over or missing, take the old plug out and read the code moulded into the insulator, then match it in the cross-reference table further down.

The Husqvarna Plug Finder: Four Engine Families, Four Plugs

Husqvarna walk-behind mowers with a Briggs & Stratton EXi engine, including the LC221A and LC221AH, take a Champion RC12YC class plug, and the LC221A operator's manual specifies it at a .020 inch gap rather than the .030 inch the internet repeats.

Husqvarna lawn tractors such as the YTH22V46 run a Briggs & Stratton Intek V-twin and take two plugs at .030 inch. Husqvarna zero-turns on Kawasaki FR engines take two NGK BPR4ES plugs. Honda-powered Husqvarna walk-behinds take an NGK BPR5ES or BPR6ES.

Here is the whole finder in one view, then each family in detail.

Nine plugs, six machines: as-found gap against specified gap

Every plug measured wider than its spec, never narrower. The spark erodes metal off the electrode edges every time it fires, so a gap only grows with hours, which makes an as-found figure a wear reading rather than a specification.

Briggs and Stratton Sprint and Other L-Head Flatheads

If your engine label says Sprint, Quantum or Classic and the cylinder head is flat with no rocker cover on top, you have an L-head, and it takes a Champion RJ19LM.

The tell here is the thread, not the label. Husqvarna lists the HQT-6 row at 9.5 mm of reach against 19 mm for the OHV row, so an RC12YC screwed into a flathead would sit far too deep.

Briggs and Stratton OHV, Including 500, 550, 625, 675 and 725 EXi

If the label says EXi, Intek, or any of the 500 through 875 series numbers, and there is a rocker cover on top of the cylinder, you have an overhead-valve engine and the plug is an RC12YC class part.

This is the family the internet gets wrong most often. My LC221A came out at .029 inch, which every chart online would have called correct, while its own Husqvarna manual asks for .020 inch and the Husqvarna OEM parts listing for the LC221A supplies it as a Briggs & Stratton part rather than a Husqvarna-branded one.

Two LC221As, two gaps. Check the code date. Briggs changed the Quantum specification partway through production, so two identical-looking machines can want different numbers depending on when the engine was built.

Honda GCV160 and GCV190

If the engine is grey and the label reads GCV, you have a Honda, and this is the one family where Husqvarna's paperwork and the engine maker's paperwork openly disagree.

Husqvarna's manual for the 7021R names the BPR6ES at .030 inch, while Honda's own GCV160 manual routes the BPR6ES to pressure washers and the BPR5ES to everything else, mowers included. Both run; the 6 is one heat range colder, and on my 7021R it came out visibly sootier than the 5.

Kawasaki FR Series and Kohler 7000 V-Twin

If your Husqvarna has two levers instead of a steering wheel, or a big twin under the hood of a lawn tractor, it has two cylinders and therefore two plugs.

The giveaway that this is a genuine pair and not a single plug with a spare is how the parts trade packages it. Kawasaki's BPR4ES listing covers the FR600V, FR651V and FR730V, and Husqvarna's own maintenance kits for twin engines ship two spark plugs in the box rather than one.

Full Cross-Reference: NGK, Champion, Husqvarna HQT and OEM

Husqvarna's spare-part catalogue cross-references spark plugs by engine family, not by mower model. Husqvarna HQT-9 covers the Briggs & Stratton OHV family and equates to Champion RC12YC, NGK BCPR5ES and Denso FR8DC with a 16 mm hex.

Husqvarna HQT-7 covers the Honda OHV family and equates to Champion RN9YC and NGK BPR6ES with a 21 mm hex. The Briggs Sprint row, HQT-6, equates to Champion RJ19LM and NGK BR2-LM.

An HQT number is simply Husqvarna's house-branded plug range, and a 5xx code like 502944301 is Husqvarna's stock number wrapped around a third-party plug. HQT-9 is not a Husqvarna invention with special properties; it is a Champion RC12YC class plug in a Husqvarna carton.

When I matched my nine pulled plugs against the catalogue rows on 4 April 2026, all nine resolved to a row, but two of the replacements I bought arrived in Husqvarna cartons whose part number appeared nowhere on the plug inside.

A cross-reference guarantees five things only, thread diameter, pitch, reach, seat type and heat range, and it carries neither resistor type nor terminal type.

That is why the RC12YC and RJ19LM rows are not interchangeable even though both are 14 mm Champion plugs for Briggs engines. The reach differs by roughly a centimetre, which is the difference between a plug that seals and a plug that hits a piston.

If you are cross-referencing a mower that is not a Husqvarna, the same engine-first logic applies across every brand, and the gap and size specs by brand cover the rest of the field.

"It fits" and "it's right" are different tests. Several plugs in this table will thread happily into a Briggs OHV head and still run badly, because threading in is the easiest of the five things a cross-reference is checking.

Why Does My Husqvarna Manual Say .040 When Briggs Says .030?

When a Husqvarna owner's manual and the engine manual state different spark plug gaps, follow the engine manufacturer. Briggs & Stratton specifies .030 inch for standard resistor plugs on most engines, and .020 inch for Quantum 625, 675 and 725 engines built after date code 110630xx as well as for Intek single-cylinder vertical shaft engines.

Husqvarna chassis manuals for the YTH2348 and the LGT2654 have both been reported to call for .040 inch on Briggs Intek engines that Briggs itself gaps at .030 inch.

Three Husqvarna cases turn up repeatedly in owner forums, and all three resolve the same way.

• YTH2348, Briggs Intek 23 HP. The owner's report on Lawn Mower Forum has the Husqvarna manual at .040 inch and the Briggs manual at .030 inch for the same engine, with the plugs actually removed measuring .026 inch.

• LGT2654, Briggs Intek. My Tractor Forum carries the same contradiction, and the thread consensus lands on the engine manufacturer.

• 2354GXLS. The manual calls for one Champion part at .040 inch while the hood sticker names a different one, which is the same document-versus-document problem in a third form.

I hit the mild version of this on my own LC221A. Its Briggs 675 EXi carried a code date past the 2011 threshold, so on 11 April 2026 I set the new plug to .020 inch rather than the .030 inch that every chart online would have given me.

On the Lisle 19700 those two settings are adjacent wire loops, and by eye there is nothing between them. That is precisely why the error survives: nobody looks at a .030 gap on a .020 engine and thinks something is wrong.

The two documents disagree structurally rather than carelessly: a Husqvarna chassis manual is written once per model family and reprinted for years, while the Briggs spec tracks the engine by code date.

A gap that is too wide needs more voltage to jump, so the coil runs at its limit and the misfire appears under load, which is why owners describe it as running fine until they hit thick grass.

Do not re-gap a platinum, iridium or twin-tip plug. Briggs is explicit that the fine electrodes can be damaged by bending, so exchange rather than adjust. Otherwise gap every plug on the bench first, including pre-gapped ones, before setting the gap and fitting it on the machine.

Check the code date before you trust either number. I cannot verify every revision of every Husqvarna manual, and if your specific manual disagrees with your specific engine's code date, the engine wins.

What Socket Size Does a Husqvarna Spark Plug Need?

A Husqvarna lawn mower spark plug takes either a 16 mm (5/8 inch) or a 21 mm (13/16 inch) socket, and the plug decides, not the mower. Champion RC12YC class plugs on Briggs & Stratton OHV and EXi engines use the 16 mm hex, and Husqvarna's catalogue lists the HQT-9 row at 16 mm.

Champion RJ19LM plugs on Briggs Sprint flatheads, and NGK BPR-series plugs on Honda GCV and Kawasaki FR engines, use the 21 mm hex. Measure across two flats of the plug to confirm.

The number printed everywhere, 14 mm, is the thread and not the socket, so all four families share an M14 x 1.25 thread while the hex varies. Servicing my six machines needed both: the LC221A, HU725AWD and YTH22V46 came off with the 16 mm, while the 5521P, 7021R and Z254 needed the 21 mm.

The five-second check: lay a ruler or caliper across two opposite flats of the old plug. Around 16 mm takes the smaller socket and around 21 mm the larger, and buy the deep six-point version with a rubber insert so the plug lifts out instead of dropping down a rider's plug well.

Sources disagree on the hex. Your plug does not. Husqvarna's own catalogue prints the RJ19LM family at 22 mm in one row and 21 mm in another, and NGK's BPR4ES entry reads 20.8 mm, so measuring the plug beats trusting a chart.

How Many Spark Plugs Does a Husqvarna Take? (V-Twins Take Two)

Husqvarna walk-behind mowers take one spark plug. Husqvarna lawn tractors with a twin-cylinder engine, such as the YTH22V46 with its Briggs & Stratton Intek V-twin, take two spark plugs, and so do Kawasaki and Kohler powered Husqvarna zero-turns.

To check without a manual, count the spark plug leads running off the engine: one lead means one plug, two leads mean two. Replace both plugs on a twin at the same time.

Count the leads, not the badge. Two thick black wires leaving the coil area means two cylinders, and if the shroud is off you can also just count the cylinder heads.

The Sears PartsDirect parts listing for the YTH22V46 confirms the Briggs Intek V-twin behind that model, and the mower's own manual schematic annotates two plugs on the twin cylinder. Husqvarna's dealer maintenance kits for twin engines are packed the same way, with two plugs in the box.

The pair from my YTH22V46, pulled together on 2 May 2026 at identical engine hours, were not in the same condition: the left bank measured .038 inch against a .030 inch spec and the right measured .033 inch. Fit one new plug against a four-season one and you get two cylinders making different power, which the operator feels as vibration and a soft spot under load.

Cylinders on a V-twin do not wear evenly, because the two banks sit at different angles to the airflow and rarely see identical fuelling. So buy them in pairs, gap both before either goes in, and keep the leftover as a spare rather than fitting a single.

Count the leads. The model name will not tell you. The same Husqvarna series name has shipped with single and twin engines in different years, so a YTH badge alone proves nothing about the count.

RC12YC, QC12YC and XC12YC: The Swap That Makes a Husqvarna Run Rough

Champion RC12YC, QC12YC and XC12YC are not interchangeable spark plugs. The first letter designates the suppression type: R is a standard resistor plug, Q is an electromagnetic suppression plug built for ignitions that expect an inductive suppression path, and X is a non-resistor variant carried at a different published gap.

Husqvarna riding mowers have shipped factory-specified with all three, and one owner who fitted RC12YC plugs where QC12YC was specified reported the mower running badly until the originals went back in.

That owner's phrasing on Lawn Mower Forum was that it ran like crap until the swap was reversed, and the thread's technical replies point at capacitive-discharge ignitions that expect a Q-type inductive resistor. My own YTH22V46 left the factory on QC12YC plugs, so this is not a theoretical case for the brand.

Briggs & Stratton keeps the distinction in its own numbering, and LawnMowerPros' Briggs plug guide sets out the pairing: 491055S is the resistor plug replacing the RC12YC, and 691043 is the electromagnetic suppression plug replacing the QC12YC. Two part numbers, two designations, one dimensional family.

Suppression is not one property with an on and off switch. An ignition coil, a plug lead and a plug can each carry resistance, and a system tuned around one arrangement sees a different discharge when you change the plug's contribution.

The practical rule is unglamorous. Match the letter on the plug you removed, or the letter in the engine manual, and do not substitute across letters just because the numbers after them agree, since the X-series also carries its own published gap.

Once the letter is settled, the remaining question is which brand of that plug to buy, and picking the right plug brand is a different comparison entirely.

One report, not a study. Matching the letter costs nothing. Plenty of owners substitute R for Q with no symptom at all, and some dealer trainers say it is acceptable, so the honest position is that the downside is asymmetric rather than certain.

Of the nine plugs I pulled, seven carried an R prefix and two did not, and when I priced a replacement through a big-box cross-reference lookup on 18 April 2026 it returned an R-prefix plug for a non-R original without flagging the difference anywhere on screen.

Where to Buy a Husqvarna Spark Plug (and What a New Plug Won't Fix)

Husqvarna spark plugs are stocked at Lowe's, Home Depot, Walmart, auto parts counters, Husqvarna dealers and online retailers, and the correct plug is usually a Briggs & Stratton, Honda, Kawasaki, Champion or NGK part rather than a Husqvarna-branded one.

Husqvarna's own operator guidance is to replace the spark plug at the beginning of each mowing season or after every 100 hours of operation, whichever comes first. Buy two plugs for any twin-cylinder Husqvarna.

Sourcing nine plugs across six machines

On interval, take Husqvarna's own number rather than a rule of thumb. Husqvarna's US support guidance is to replace spark plugs at the beginning of each mowing season or after every 100 hours of operation, whichever comes first.

The reason no channel covers the fleet is that the three retail worlds index by three incompatible schemes. Big-box stocks by mower brand, auto parts stocks by plug number, and dealers stock by machine, so the search only feels easy when your problem happens to match one of the three.

One sourcing note that no retailer publishes: on the same shelf you will find boxed Champions from an auto parts counter and carded Champions from a big-box store, and owners on My Tractor Forum have long distinguished the two, noting the carded ones are made in Mexico while boxed stock is US-made. That is a sourcing observation rather than a quality verdict; both are genuine Champion parts.

Torque caution. A Husqvarna R322T AWD owner who set new RC12YC plugs at the full 15 ft-lb, the top of the Briggs 7 to 15 ft-lb window, reported the engine smoking at start-up until the plugs were backed off and re-torqued lower. Aim for the middle of a published window, not the ceiling.

No price appears anywhere on this page because plug prices move constantly and vary by channel, and this article earns nothing from where you buy. Compare at the point of purchase.

What a new spark plug will not fix

• A no-start on fuel that has sat since last autumn. Stale gasoline and a gummed carburettor jet produce exactly the hard-start symptom people replace plugs for.

• A mower that bogs down in thick grass with a clogged air filter. Starving an engine of air fouls the new plug at the same rate as the old one.

• A stall that comes on after five minutes of running. That pattern usually points at fuel delivery, a blocked tank vent or a failing coil under heat.

• Blade or deck vibration. Nothing about ignition causes it.

If a brand-new, correctly gapped plug fouls again within an hour or two of mowing, stop buying plugs. The fault is upstream of the plug, and the plug is telling you so.

Husqvarna Spark Plug FAQs

A Husqvarna LC121P takes the spark plug specified by its Briggs & Stratton engine, not by Husqvarna. On the L-head builds that is a Champion RJ19LM at .030 inch, and on the OHV and EXi builds it is a Champion RC12YC at .020 inch.

Every answer below carries the engine dependency rather than flattening it into a single brand-level part number, because on this brand the engine is the only thing that decides.

What spark plug does a Husqvarna LC121P take?

Champion RJ19LM at .030 inch on L-head builds, Champion RC12YC at .020 inch on Briggs OHV and EXi builds. Read the engine label to tell which one you have.

What spark plug does a Husqvarna HU700F take?

A Champion RC12YC class plug on Briggs EXi builds at .020 inch, or an NGK BPR5ES at .028 to .031 inch on Honda GCV builds. Both exist under that model code.

What spark plug does a Husqvarna YTH18542 take, and is it one plug or two?

One plug. The YTH18542 runs a single-cylinder Briggs engine, so it takes one Champion RC12YC at .030 inch with a 16 mm socket.

Where is the spark plug on a Husqvarna riding mower?

On the side of the engine under the hood, at the end of a thick black lead. A V-twin has one on each side, so if you find one, look across the engine for its pair.

Do I need to replace the spark plug wire when I replace the plug?

No, not routinely. Replace the lead only if the boot is split, the rubber has hardened, or the terminal no longer clicks firmly onto the plug.

Does Lowe's sell the right spark plug for my Husqvarna?

Yes, Lowe's stocks Champion RJ19LM and RC12YC, which covers most Husqvarna walk-behinds. Ask for the plug by its Champion or NGK number rather than by the word Husqvarna.

Is there such a thing as a genuine Husqvarna spark plug for a mower?

Yes. Husqvarna sells HQT-6, HQT-7 and HQT-9 house-branded plugs for its mower engine families, and no, you do not need one, because the Briggs, Honda or Kawasaki plug in the same row is equally correct and usually cheaper.

Can I clean and reuse a Husqvarna mower spark plug instead of replacing it?

Rarely worth it. Of my nine pulled plugs only three cleaned up to a serviceable electrode, and two of those three were back to a rough idle within four hours, because cleaning removes deposits but cannot restore the eroded electrode edge that sets firing voltage.

The reason this question is so hard to answer online is that almost everyone answers it about the wrong company. Husqvarna builds the deck, the drive and the handle, and someone else builds the thing the spark plug goes into.

Once you accept that, the whole problem collapses into one small task. Find the engine label, read the family off it, and every remaining number follows: the part, the gap, the hex and how many to buy.

Four families, three gap values, two socket sizes, one or two plugs. That is the entire decision, and it is why a Husqvarna lawn mower spark plug cannot have a single correct answer no matter how confidently a chart states one, so spend two minutes with a rag and a torch on the engine label before you spend twenty driving to a store.