Pro Circuit 304 Factory Sound Silencer
MSRP: $169.95
$135.96
Exact Fitment Guarantee
The Pro Circuit 304 Factory Sound Silencer is the benchmark two-stroke performance silencer engineered to replace heavy, restrictive stock mufflers on modern two-stroke motocross and enduro machines. Featuring a slightly longer body section than shorty supercross silencers, the 304 Factory Sound strikes the ultimate balance between crisp throttle response, broadened mid-to-top power delivery, and an iconic, crisp two-stroke exhaust note that thrills riders without producing unbearable high-frequency ear fatigue.
The canister body is extruded from lightweight, high-grade 6061-T6 aluminum with a brushed clear-anodized finish that resists corrosion and exhaust residue staining. The intake stinger tube and CNC-machined end cap are fabricated from durable stainless steel to resist exhaust vibration fatigue and heat cracking. Double-walled mounting brackets are welded directly to the canister for maximum structural rigidity under severe off-road vibration. On the track, the 304 silencer noticeably sharpens throttle response right off the bottom and allows the two-stroke powerband to pull cleanly through the midrange into extended top-end over-rev.
- Canister Material: Extruded 6061-T6 brushed aluminum
- Inlet Stinger & End Cap: 304 stainless steel construction
- Core Design: Perforated steel straight-through competition core
- Mounting: Double-walled reinforced TIG-welded aluminum brackets
- Sound Profile: Factory crisp two-stroke acoustic resonance
### Step-by-Step Installation & Safety Protocols Installation is exceptionally simple. Remove the right-side plastic number plate. Loosen the rubber joint coupler clamp connecting the pipe stinger to the silencer. Remove the two subframe mounting bolts and slide the stock silencer off. Inspect the rubber exhaust coupler and replace if torn or brittle. Apply a light dab of silicone grease to the inside of the rubber coupler, slide the Pro Circuit 304 inlet into the coupler, and line up the mounting brackets with the subframe tabs. Secure the mounting bolts to 18-20 Nm and tighten the hose clamp on the rubber sleeve. Ensure the silencer canister has adequate clearance from the rear brake caliper through the full suspension stroke.
### Maintenance & Repacking Schedule Maintenance requires repacking the silencer with two-stroke fiberglass packing cartridge every 20-30 operating hours, as two-stroke unburnt premix oil gradually saturates the packing material, degrading acoustic dampening and engine performance.
Frequently Asked Questions
Q: How does the 304 Factory Sound differ from the Pro Circuit R-304 Shorty?
A: The standard 304 Factory Sound has a longer aluminum body designed for all-around motocross and off-road power delivery with broad top-end over-rev, whereas the R-304 Shorty has a condensed canister tuned for explosive bottom-to-mid punch on tight supercross tracks.
Q: Will the 304 silencer bolt onto my stock OEM two-stroke expansion chamber?
A: Yes. The Pro Circuit 304 silencer is engineered to bolt directly onto the factory OEM pipe as well as aftermarket Pro Circuit Works and Platinum expansion chambers.
Q: How do I know when my two-stroke silencer needs repacking?
A: Key symptoms include a noticeably louder, harsher exhaust tone, oil weeping heavily from the end cap rivets, and a loss of crisp throttle response due to oil-saturated packing material restricting core flow.
Q: Does this silencer include a spark arrestor?
A: No. The 304 Factory Sound is an open competition silencer; for a USFS-approved spark arrestor, consider the Pro Circuit Type 296 or Nature Friendly silencer models.