Briggs & Stratton Crankcase Oil Seal - 399781S

Product Details & Features

Keep your Briggs & Stratton engine sealed and running without messy oil leaks with this genuine crankcase oil seal (Part 399781S) — a precision‑engineered OEM replacement designed to protect your engine’s internal lubrication system.

This 399781S oil seal acts as a tight seal around a rotating shaft (such as the crankshaft or PTO shaft) where it exits the crankcase, helping prevent engine oil from leaking while keeping dirt and contaminants out of the engine internals. It’s made from oil‑resistant elastomer with metal reinforcement to withstand typical small‑engine operating conditions and deliver long‑lasting performance. 

Key Features:

• Genuine OEM Part: Manufactured by Briggs & Stratton to original equipment specifications for accurate fit and reliable sealing performance.

• Precision Seal: Designed to maintain a secure oil barrier around crankcase openings where the shaft passes through, helping support proper lubrication and prevent leaks. 

• Durable Construction: Oil‑resistant synthetic rubber with metal reinforcement withstands oil exposure, engine vibration and typical temperature cycles. 

• Direct Replacement: Replaces older part numbers such as 399781 and fits many Briggs & Stratton engines including Intek™, Quantum, DOV and other series used on lawnmowers and outdoor power equipment. 

• Easy Install: Designed for straightforward installation during crankcase service, rebuilds or when replacing worn or leaking seals. 

Why It Matters:
Over time, oil seals can harden or wear, leading to oil seepage around the crankcase or PTO shaft — a common cause of messy leaks and premature wear. Installing this genuine 399781S crankcase oil seal helps restore a proper oil‑tight seal, supporting stable lubrication, smoother engine operation and longer component life.