FMF 4 Stroke Exhaust Wash Plug

The FMF 4-Stroke Exhaust Wash Plug (011299) is a tapered rubber muffler seal engineered to block water, soap, and condensation from entering the exhaust system during motorcycle washing, storage, and transport. Modern 4-stroke off-road, dual-sport, and adventure mufflers feature large-diameter straight-through perforated cores wrapped in fiberglass sound-absorbing matting. Spraying high-pressure water into the muffler outlet saturates the packing material—destroying its acoustic dampening properties and inducing premature blowout—while allowing water to pool in header low points or migrate past open exhaust valves directly into the combustion chamber and crankcase oil.

Molded from flexible, heavy-duty synthetic rubber with a multi-ribbed conical profile, the 011299 plug compresses securely into exhaust outlets ranging from 33mm to 60mm in inner diameter. It creates a watertight barrier that withstands pressure washer spray and prevents moisture intrusion from ambient humidity changes during storage. A high-visibility woven FMF warning streamer is tethered to the plug via a metal keyring to serve as a clear visual reminder to remove the plug before starting the engine.

Features:

• Watertight Tapered Rib Design: Stepped conical rubber ribs compress to seal muffler exit bores from 33mm to 60mm, preventing water from saturating internal fiberglass packing or reaching exhaust valves.

• High-Visibility Warning Streamer: Attached bright FMF fabric ribbon alerts riders to remove the plug prior to starting the motorcycle, preventing exhaust backpressure blowouts.

• Heavy-Duty Elastomer Construction: Formulated from durable, oil- and chemical-resistant molded rubber that maintains elasticity across wide temperature swings without cracking.

• Universal 4-Stroke Fitment: Fits both OEM stock silencers and aftermarket slip-on or full-system exhausts across 250cc to 1300cc+ four-stroke platforms.

• Condensation & Pest Barrier: Seals the exhaust tract during winterization, trailer transport, or humid garage storage to prevent internal corrosion and rodent nesting.

• Integrated Metal Keyring Tether: Corrosion-resistant ring secures the warning streamer firmly to the plug base for easy extraction.

What's in the Box:

• 1x FMF 4-Stroke Tapered Rubber Exhaust Wash Plug (Part #011299)

• 1x Pre-Attached FMF High-Visibility Warning Streamer & Keyring

Fitment Notes:

• Exhaust Outlet Compatibility: Fits round and oval muffler exhaust outlets with an internal diameter (ID) between33mm (1.30 in) and60mm (2.36 in).

• Motorcycle Platforms: Compatible with 4-stroke motocross, cross-country/enduro, dual-sport, and adventure motorcycles (including FMF Q4, Powercore 4, Factory 4.1, and OEM mufflers).

• Spark Arrestor & Quiet Core Note: Compatible with most mufflers running standard USFS screen-type spark arrestors or quiet inserts, provided the exit aperture is at least 33mm in diameter.

• 2-Stroke Fitment Note: For smaller-bore 2-stroke silencers (typically 22mm to 33mm ID), use the FMF 2-Stroke Exhaust Wash Plug (Part #011300).

• Exhaust Cool-Down Rule (Preventing Melted Rubber): Never insert a rubber wash plug into a hot muffler immediately after riding. Four-stroke titanium and stainless steel end caps routinely exceed 350°F–450°F after trail or highway use. Inserting the plug while the metal is hot will melt the rubber ribs onto the end cap, ruining the seal and leaving scorched residue on the exhaust tip. Always allow the exhaust system to cool to ambient temperature before inserting the plug and starting your wash routine.

• Projectile Warning: Always heed the warning streamer. If you forget to pull the plug and manage to kick the bike over with a strong spark, the engine compression will fire that rubber plug out of the exhaust tip, potentially damaging whatever is parked directly behind your motorcycle in the garage.

Part Number: 011299