Briggs & Stratton Quantum XTL 55 I/C (Model 129802) - Specs and Service Data
The Quantum XTL 55 I/C - the definitive 1990s-2000s walk-behind mower engine, from Briggs series documentation.
Specs last verified Oct 28, 2026 against the sources shown.
Full specifications
Specifications grouped by system.
01 Engine
- Bore x Stroke68.3 x 51.99 mm (Briggs & Stratton)
- ConfigurationL-head (flathead), single cylinder, vertical shaft, air-cooled (Briggs & Stratton)
- Displacement190 cc (Briggs & Stratton)
- Power5.5 HP (gross) (Briggs & Stratton)
02 Dimensions and Mounting
- Dry weight24.3 lb (11.0 kg) (Briggs & Stratton)
03 Capacities and Service
- Oil capacity18-20 oz (Briggs & Stratton)
Service data
Service specifications for rebuilds and tune-ups.
- Valve clearance - intake0.005-0.007 in (Briggs & Stratton)
- Valve clearance - exhaust0.007-0.009 in (Briggs & Stratton)
- Cylinder head bolt torque140 in-lb (Briggs & Stratton)
- Spark plug gap0.030 in (Briggs & Stratton)
- Oil typeSAE 30 or 10W-30 (5W-30 below 40 F) (Briggs & Stratton)
Service figures are for this model stamp as published - check your operator manual before a rebuild.
Find and decode your stamp
This engine's stamp reads: Model 129802, the Code is stamped per engine and gives its build date.
On Quantum L-head engines the Model-Type-Code is stamped into the blower housing - the metal shroud over the flywheel - most often along the top edge of the housing or the side facing the muffler; some builds carry the same numbers on a metal tag riveted to the housing. (Per Briggs & Stratton identification literature for single-cylinder L-head engines and repair manual 270962.). Bring the full stamp - model, type, and code - to the decoder.
Read the Quantum decode page or paste the whole stamp into the Briggs & Stratton decoder for the build date and what each part means.
Repower - what it replaces
Briggs published factory replacement mappings for parts of this series (form MS-1060 covers the 12H802/12H807 Types); modern EXi-class engines are the current-production repower path for this footprint. Shaft is Type-dependent - match the full Model-Type before ordering.