Description
If you’re running a stock 883cc or 1200cc Big Twin, you’re leaving significant power on the table. The S&S CYCLE Piston Kit 106-3690 bumps displacement to 1250cc while maintaining reliable 10.3:1 compression, delivering a straightforward path to increased displacement without major engine architecture changes. This is a proven, bolt-on upgrade that works with both stock and performance heads—giving you measurable performance gains on the dyno and the street.
- Displacement: 1250cc
- Compression ratio: 10.3:1
- Piston design: Cast flat-topped
- Bore size: 3-9/16″
- Fitment: 1984–’99 HD Big Twins
- Compatible cylinders: Stock 1200cc, 1986–’2003 883cc (bored)
- Head compatibility: Stock heads supported
- Recommended: S&S CNC ported heads
- Installation: Requires cylinder boring
- Not compatible: 2004–’16 883cc cylinders
