MCS Breather Valves

9 products — part of all Breather Valves

MCS breather valves give Harley-Davidson engine builders direct-fit replacement components that regulate crankcase pressure on Big Twin and Sportster engines, preventing oil mist from contaminating the air cleaner and ensuring efficient engine breathing under all operating conditions. The breather valve allows blowby gas to vent from the crankcase while preventing oil from exiting — a valve that sticks open saturates the air cleaner element with oil, causing a rich running condition and visible smoke from the air cleaner. A valve that sticks closed builds crankcase pressure that forces oil past gaskets and seals throughout the engine. MCS supply breather valves to the dimensional and flow specifications of the main Harley-Davidson breather configurations used across Big Twin and Sportster engine generations, providing direct-fit replacements that restore correct crankcase pressure regulation without modification. Iron City Motorcycles, an authorised Harley-Davidson dealer in Leeds, stocks MCS breather valves alongside a full engine lubrication and breathing components range. Browse the full MCS Breather Valves range below.