Briggs & Stratton (B&S) 490420 12V 16-tooth single-cylinder air-cooled engine with permanent magnet direct-drive starter motor

12V permanent-magnet direct-drive starter motor built for 11-16 HP single-cylinder lawn equipment. High-induction magnets and copper windings deliver strong cranking even in cold weather, the 16-tooth nylon-composite gear protects aluminium ring gears, and the sealed housing resists dust, clippings and damp storage.

OEM and Search References

• Primary reference: Briggs & Stratton 490420
• Substitute reference: Briggs & Stratton 393499 / 394943 / 399169 / 494148 / 494198 / 494490 / 494990 / 497401 / 499521 / 499529 / 691262 / 795121, LG490420 / LG497401 / LG499521; John Deere AM106883 / AM38136 / AM39285; MIA11175 / MIU13772; Lester 5742 / 5746 / 5778
• Equipment reference: Briggs & Stratton 11-16 HP single-cylinder air-cooled engines (Intek, Powerbuilt, I/C series) on lawn tractors and riding mowers, including Cub Cadet GMT-125 and the John Deere models listed against AM106883 / AM38136 / AM39285
• Buyer search terms: Briggs & Stratton 490420 starter motor, 490420 starter, 16 tooth starter, nylon gear starter, Intek starter motor, Cub Cadet GMT-125 starter, 12V lawn tractor starting motor

Reference Specifications

• System voltage: 12V, permanent-magnet direct-drive (PMDD) design
• Pinion: 16 teeth, nylon-composite drive gear (for aluminium ring gears only)
• Power: 0.6-0.7 kW
• Housing length: approximately 101.6 mm (4 in); mounting centres approximately 57 mm (2.25 in)
• Rotation: counter-clockwise (CCW), viewed from the pinion end
• Important identification note: the 490420 uses a longer housing (about 101.6 mm) than the 497595 (about 92 mm) and is the higher-torque of the two. The 16-tooth nylon gear must never be run against a cast-iron ring gear, and it does not interchange with the 15-tooth steel gear of the twin-cylinder 691564.

Fitment and Purchase Checks

Catalog-listed equipment: 11-16 HP Briggs & Stratton single-cylinder air-cooled engines and the lawn tractors listed above. Confirm engine model and type code, existing starter number, voltage, pinion tooth count (16 teeth), drive-gear material, rotation, mounting centres (57 mm), terminal type and physical dimensions before purchase. Check the flywheel ring gear material as well: nylon gears are for aluminium ring gears, steel gears for cast iron. Exact fitment on unlisted models has not been verified and is omitted.

For Agricultural Buyers and Distributors

This listing is organized for outdoor power equipment procurement teams, repair shops and parts distributors searching by engine model and OEM reference. It covers the 11-16 HP single-cylinder Intek / Powerbuilt range, one of the largest installed bases in residential mowing, and the numbers also cross to John Deere AM106883 and the Lester 5742 family. For quotation, specify the engine model, old-part number, required quantity and destination. Confirm price, stock, package quantity and delivery terms with the seller before placing purchase order.

Product Positioning

Briggs & Stratton 11-16 HP single-cylinder engines power an enormous fleet of residential lawn tractors and riding mowers, and the starter is among the first electrical parts to fail on machines that start and stop dozens of times per session. Owners then face a wall of similar-looking numbers: 490420, 497401, 494990 and the rest all fit the same block but differ in housing length and gear material. This starter reproduces the original 16-tooth gear, 2-bolt flange at 57 mm centres and single B+ stud exactly, so a workshop replaces the unit as a whole instead of rebuilding a worn one. For distributors, it is a steady-turnover item across the Intek / Powerbuilt range and cross-lists to John Deere, which widens the customer base from one SKU.

How It Works: Power and Engagement

The unit is a permanent-magnet direct-drive (PMDD) design: a copper-wound armature spins inside high-induction permanent magnets, and the 16-tooth gear is fixed to the armature shaft through a Bendix drive, so cranking is immediate when current flows. Turning the key applies battery voltage to the B+ stud; the Bendix throws the gear into mesh with the ring gear as the armature accelerates, then retracts it once the engine fires - a purely mechanical sequence with no external solenoid to fail. Rotation is counter-clockwise viewed from the pinion end, matching the Briggs flywheel. The 2-bolt flange at 57 mm centres fixes the gear-to-ring-gear clearance exactly as the factory unit did, which keeps engagement quiet and complete.

Materials and Durability

• Drive gear: 16-tooth nylon composite, quiet running and non-scoring on aluminium ring gears.
• Magnets: high-induction permanent magnets, stable at engine-bay temperature and resistant to demagnetization.
• Windings: pure copper wire for low resistance and good heat rejection through repeated start cycles.
• Brushes and commutator: wear-resistant carbon brushes in a sealed housing that keeps clippings and dust away from the contact area.
• Housing: sealed, corrosion-resistant shell with 101.6 mm body, built for rain, wash-down and year-round outdoor storage.

Problems It Solves

These tractors usually arrive with one of four complaints. First, slow cranking that worsens when hot, from weak magnets or worn brushes in the original. Second, a grinding rattle from a Bendix that no longer throws the gear fully into mesh. Third, intermittent no-start from arced or contaminated commutator surfaces. Fourth, a starter that spins but does not turn the engine, typically a sheared or stripped nylon gear. Replacing the complete unit clears all four in one step. Two cautions before ordering: match the housing length (101.6 mm here, not the 92 mm 497595) and confirm the ring gear is aluminium - a nylon gear run against cast iron will strip in days.

Replacement Value for Shops and Distributors

For repair shops, one correctly matched starter returns the mower to work the same day, with no drilling, tapping or wiring changes in between. For dealers and distributors, the numbers work: 50-unit minimum order, 7-30 day lead time, 12-month warranty, and unit pricing well below OEM supply channels, leaving room for margin at a competitive shelf price. Production follows ISO 9001, IATF 16949 and CE practices, and consistent cross-references to Lester 5742, John Deere AM106883 and LG497401 keep ordering by catalog number straightforward and returns low.