6 Best Lawn Mower Won’t Start Spark Plugs (2026): Our Picks

By Graham Fisher

Updated November 2026

When a lawn mower won’t start, the spark plug is one of the first parts worth checking, and one of the cheapest to replace. A fouled, worn or wet plug can stop an engine cold, but the replacement has to match the thread size, reach, gap and heat range your engine expects. The six spark plugs below were selected by checking manufacturer fitment data, brand reputation and the patterns owners commonly report, with a focus on Briggs & Stratton-style small engines, a Honda mower engine and one Yard-Man-style application. We did not test these plugs ourselves; the notes reflect listing details and published specifications.

Our Top Picks

Quick Comparison

Briggs & Stratton 796112-2pk Spark Plug (2 Pack)

Briggs & Stratton 796112-2pk Spark Plug (2 Pack) Replaces J19LM, RJ19LM, 802592, 5095K by Briggs & Stratton

View on Amazon

Best for: Most Briggs & Stratton walk-behind mowers that list the older J19LM or 802592 part numbers.

This is a good fit for owners who have an engine cover or manual pointing to one of the cross-referenced numbers and want a plug that lines up with that reference. Two plugs in the pack give you a spare for the next season.

Key specs

• Sold as a 2-pack
• Listing cross-references J19LM, RJ19LM, 802592 and 5095K
• Briggs & Stratton branded

Pros

• Multiple cross-references make part matching easier
• Brand matches the engine most owners are working on
• Two-pack covers a spare

Cons

• Cross-references are only a guide; confirm the thread and reach against your old plug
• Not a fit for Honda or non-Briggs engines

Bottom line: A strong default choice for a Briggs & Stratton owner who wants an easy part-number match and a spare.

View on Amazon

Briggs & Stratton 491055-2pk Spark Plug (2 Pack)

Briggs & Stratton 491055-2pk Spark Plug (2 Pack) Replaces 805015/72347/491055/Champion RC12Y

View on Amazon

Best for: Owners matching an engine that lists 491055, 805015 or 72347 as the original plug.

The listing ties this plug to a Champion RC12Y equivalent, which helps if you are comparing across brands. It suits a mower where the original plug is hard to read or already discontinued.

Key specs

• Sold as a 2-pack
• Listing cross-references 805015, 72347, 491055 and Champion RC12Y
• Briggs & Stratton branded

Pros

• Useful cross-reference to a common Champion equivalent
• Two plugs in one pack
• Easy to match if the old plug is worn beyond reading

Cons

• Cross-reference list is long, so verify the exact part number on your old plug
• Gap should be checked against your engine manual before installing

Bottom line: Best for owners who want a plug that bridges Briggs & Stratton and Champion part numbers.

View on Amazon

Replacement 692051 499608 Spark Plug for Briggs & Stratton Lawn Mower Models

Replacement 692051 499608 Spark Plug for Briggs & Stratton Lawn Mower Models

View on Amazon

Best for: A budget replacement for Briggs & Stratton mowers that call for 692051 or 499608.

This is a single-plug listing aimed at owners who only need one replacement and want to keep the cost of a routine tune-up low. It is a sensible option for an older mower with a known part number.

Key specs

• Replaces part numbers 692051 and 499608
• Designed for Briggs & Stratton lawn mower models

Pros

• Good option when you need just one plug
• Matches the 692051 part number widely used on small Briggs engines
• Easy to order against a known number

Cons

• Less brand-name documentation than the OEM-style options
• Check the heat range against your manual, since aftermarket plugs vary

Bottom line: A practical budget pick for an owner with a clear 692051 or 499608 requirement.

View on Amazon

Service part for the starting and ignition circuit on mowers and yard equipment Spark Plug For Yard Man Replaces 1716

Service part for the starting and ignition circuit on mowers and yard equipment Spark Plug For Yard Man Replaces 1716

View on Amazon

Best for: Yard-Man-style mowers and yard equipment that list part 1716.

If your mower came from the Yard-Man line or your manual references 1716, this listing is the match to check first. It is also a reasonable choice for other yard equipment with a similar ignition circuit.

Key specs

• Replaces part number 1716
• Listed for mowers and yard equipment starting and ignition circuits

Pros

• Specific match for a Yard-Man part number
• Covers a broader range of yard equipment
• Clear use case in the listing

Cons

• Limited cross-reference information compared with the Briggs listings
• Confirm thread size and reach before installing

Bottom line: The right pick for a Yard-Man owner whose part number is 1716.

View on Amazon

Honda Genuine OEM 98079-55846 Spark Plug BPR5ES

Honda Genuine OEM 98079-55846 Spark Plug BPR5ES; Replaces 98079-55876

View on Amazon

Best for: Honda-powered mowers that call for the BPR5ES spark plug.

Honda engines are specified to particular plugs, and a genuine Honda part removes most guesswork. This suits owners who want the manufacturer’s specification rather than an aftermarket equivalent.

Key specs

• Genuine Honda OEM part number 98079-55846
• Specification BPR5ES
• Replaces 98079-55876

Pros

• Manufacturer-specified plug for Honda engines
• Replaces a related part number
• Low risk of fitment surprises on a Honda engine

Cons

• Only useful on Honda engines
• Typically sold as a single plug, so no built-in spare

Bottom line: The safest choice for a Honda mower owner who wants the factory-specified plug.

View on Amazon

OEM (Pack of 2) Champion Spark Plugs for Briggs & Stratton 692051, 694385, 700646

OEM (Pack of 2) Champion Spark Plugs for Briggs & Stratton 692051, 694385, 700646

View on Amazon

Best for: Owners who want a two-pack of plugs for Briggs & Stratton engines that cross-reference to 692051, 694385 or 700646.

This two-pack suits someone who keeps a spare on the shelf and wants a plug for one of several related Briggs part numbers. It is also useful for a second mower in the same household.

Key specs

• Sold as a pack of 2
• Champion branded
• Cross-referenced to 692051, 694385 and 700646

Pros

• Two plugs for a spare or a second engine
• Covers several related Briggs part numbers
• Champion is a widely known spark plug brand

Cons

• Verify the cross-reference against your old plug before buying
• Gap should be checked against the engine specification

Bottom line: A good value for owners who want a spare and whose engine lists one of these part numbers.

View on Amazon

Buying Guide

Match the part number and thread size

Start by reading the number printed on the old plug or in the owner’s manual. Thread diameter and reach must match exactly; a plug that is too long can strike the piston, and one that is too short leaves the electrode poorly positioned. Cross-references are useful, but confirm them against the physical plug.

Good picks for this: Briggs & Stratton 796112-2pk Spark Plug and Spark Plug For Yard Man Replaces 1716

Check the gap and heat range

Gap is set in thousandths of an inch and is listed in most engine manuals. Heat range affects how the plug runs; the wrong heat range can cause fouling or pre-ignition. Use the value your engine manufacturer specifies rather than guessing.

Good picks for this: Briggs & Stratton 491055-2pk Spark Plug and Honda Genuine OEM 98079-55846 Spark Plug BPR5ES

Decide between OEM and aftermarket

OEM plugs carry the engine maker’s specification and are the simplest route when you want no surprises. Aftermarket plugs can work well when the part number and specifications are confirmed, and they often cost less per plug. Either way, buy from a seller that lists the exact part number.

Good picks for this: Honda Genuine OEM 98079-55846 Spark Plug and Replacement 692051 499608 Spark Plug

Consider how many you need

If you service more than one engine, or want to keep a spare, a multi-pack saves a second trip. A single plug is enough for a routine swap on one mower.

Good picks for this: OEM (Pack of 2) Champion Spark Plugs and Briggs & Stratton 796112-2pk Spark Plug

Check the engine brand before ordering

Briggs & Stratton, Honda and Yard-Man-style engines use different plug specifications, even when they look similar. Identify the engine brand on the shroud or in the manual first, then choose a plug that matches that brand’s listed number.

Good picks for this: Honda Genuine OEM 98079-55846 Spark Plug and Spark Plug For Yard Man Replaces 1716

Think about durability and replacement interval

Spark plugs wear with hours of use and exposure to fuel and heat. Replacing the plug once a season, or as the manufacturer recommends, is an easy habit that prevents many no-start problems. Keep the old plug as a reference for color and wear.

Good picks for this: Briggs & Stratton 491055-2pk Spark Plug and OEM (Pack of 2) Champion Spark Plugs

FAQ

How do I know if the spark plug is the problem?

Remove the plug and look at the electrode. A dry, sooty tip often points to a rich fuel mixture, while a wet, oily tip can mean oil in the cylinder. Test for spark by grounding the plug against the engine while cranking. No spark suggests a plug, coil or ignition issue.

How tight should a spark plug be installed?

Most small engines call for a specific torque, often in the range of 15 to 20 foot-pounds for many common sizes, but always check the engine manual. Overtightening can damage the threads, and undertightening can cause poor heat transfer and leaks.

Can I use a different plug than the one listed in my manual?

You can if the replacement matches the thread size, reach, gap and heat range. Cross-references help, but the manual is the authority for your engine. When in doubt, ask a small-engine service technician.

How often should I replace the spark plug on a mower?

Many owners replace the plug once a season or after about 25 to 50 hours of operation, but the manufacturer’s maintenance schedule is the best guide. Replace it sooner if the engine runs rough or is hard to start.

Why does my mower start and then die after I replace the plug?

This can point to a fuel delivery problem, a clogged carburetor or air filter, or a safety switch issue rather than the plug itself. Check fuel, air flow and the kill switch before replacing more parts.

Should I gap a new spark plug before installing it?

Many new plugs come pre-gapped, but it is worth checking with a feeler gauge against the manufacturer’s specification. Adjust only by carefully bending the ground electrode, and never touch the center electrode.

Conclusion

For most Briggs & Stratton owners, the Briggs & Stratton 796112-2pk Spark Plug is a sensible starting point because of its wide cross-reference list. If your number is 491055 or 805015, the 491055 two-pack is the closer match. Yard-Man owners should look at the part 1716 listing, Honda owners should use the genuine BPR5ES plug, and anyone on a tight budget with a clear 692051 requirement will find the replacement listing practical. Always confirm the part number, thread, reach and gap against your engine manual before installing.

Sources

• Consumer safety guidance on small engine and outdoor power equipment use (cpsc.gov)
• Background on small engine maintenance and fuel-related efficiency (energy.gov)
• Workplace guidance on safe handling and maintenance of powered equipment (osha.gov)

Related reading

• Yardworks Battery Lawn Mower Won't Start: 7 Causes and Fixes
• Yardman Riding Lawn Mower Won't Start: 7 Causes and Fixes
• Yardman Lawn Mower Won't Start: 8 Causes and Fixes (2026)

About Graham Fisher

Graham Fisher is part of our editorial team and reviews and edits our lawn mowers guides, checking product details against manufacturer specifications and owner feedback.