Oil Tank Bottom Fatboy Retro Fit Kit

The Peterson Fluid Oil Tank Bottom Fatboy Retro Fit Kit (Part Number 08-9099) is a 5-gallon dry sump oil tank system engineered for custom motorcycle builds, particularly Harley-Davidson Fat Boy models and similar large-displacement cruisers. This aluminum reservoir delivers the clean, efficient oil circulation required by modern performance engines while maintaining the classic aesthetic of retro-styled powerplants.

The kit features a 5-gallon capacity housed in an aluminum construction with natural finish, measuring 18.62 inches in height and 10.5 inches in outer diameter. Flow integration uses 10 AN male inlet and 16 AN male outlet connections, accommodating both supply and return circuits typical of dry sump configurations. An integral breather is built into the tank assembly, eliminating the need for external crankcase ventilation components and reducing system complexity. The compact footprint and proportions are optimized to integrate into Fat Boy frame geometry without requiring extensive chassis modification.

This retrofit kit addresses builders seeking reliable oil storage and circulation for custom applications where factory tanks are unsuitable or unavailable. Dry sump systems offer superior oil cooling, reduced carry-over into the combustion chamber, and engine protection during aggressive lean angles—advantages valued in both show-quality restorations and performance cruiser builds. The AN fittings provide standardized hose connection points, allowing flexible routing to match your specific frame and component layout. Natural aluminum allows for custom finishing or protection coating per builder preference.

Peterson Fluid is recognized for precision-engineered fluid storage and circulation components across marine, automotive, and powersports markets. This tank reflects the brand's focus on functional, durable design suitable for long-term service in demanding environments.