HZ GX390/GX340 Exhaust Muffler Assembly for Honda GX340 GX390 Engines — Complete Kit with Pipe, Gaskets & Hardware

HZ GX390 GX340 Exhaust Muffler Assembly is a full replacement muffler kit designed to fit Honda GX340/GX390 engines and many compatible 11–18 hp clone motors, supplying the muffler, pipe, gaskets, mounting hardware and a service spark plug.

If your Honda GX340 or GX390 engine (or a compatible clone such as a Harbor Freight Predator or other 420cc/390cc variants) needs a replacement exhaust assembly, this HZ kit provides the main muffler body, exhaust pipe/manifold, gaskets, studs and nuts required for reinstallation. It’s packaged as a practical repair solution for equipment owners who run pressure washers, water pumps, compressors, log splitters, chippers and other small-engine machinery powered by OHV horizontal engines in the 337–440cc range.

Which engines and models will this muffler assembly fit?

This HZ assembly is built to be compatible with Honda GX340, GX390, GX340T, GX390T and similar clone engines (337cc–440cc). It also fits many 11–18 hp aftermarket and OEM-equivalent engines used on commercial and consumer equipment.

• Honda part cross-references for common GX340/GX390 exhaust and manifold designs
• Fits Harbor Freight Predator 420cc and many 389–440cc clone engines
• Works with equipment from DeWalt, Simpson, Powerhorse, Mi-T-M, Excell and others

What components are included in the kit and why they matter?

The kit arrives with the assembled muffler and exhaust pipe plus the necessary mounting parts to replace the factory assembly without sourcing external pieces. Included hardware minimizes downtime and keeps installation straightforward for technicians and DIY owners.

• Muffler assembly and exhaust pipe/manifold for direct replacement
• Two exhaust gaskets and two studs for secure sealing
• Five mounting nuts and a replacement spark plug for routine service

How is this muffler used across different applications?

Designed for versatility, the HZ muffler kit suits a wide range of small-engine applications where GX-style exhausts are standard. It’s suitable for repair shops, rental fleets and individual owners replacing worn or damaged muffler assemblies.

• Pressure washers (3,600–4,400 psi machines that use GX-style engines)
• Water pumps, air compressors, log splitters, chippers and more
• Replacement on OEMs and aftermarket engines with matching flange and bore

What should I check before buying to ensure fitment?

Verify your engine model, cylinder displacement and exhaust flange pattern before ordering. Cross-reference existing part numbers and compare the exhaust outlet shape and bolt spacing to avoid mismatches.

• Confirm engine model (GX340 / GX390 / clone designation)
• Compare part numbers or measure flange bolt spacing and pipe diameter
• Inspect exhaust routing and clearance around shrouds and accessories

Who is this for: The HZ GX390 GX340 Exhaust Muffler Assembly is for mechanics, rental operators and equipment owners who need a complete, cost-effective replacement for worn or damaged GX-style mufflers. It’s particularly useful for those servicing pressure washers, pumps, compressors, log splitters and other machines using 337–440cc horizontal OHV engines. If you value an all-in-one repair kit that includes gaskets and mounting hardware, this assembly reduces parts sourcing and simplifies reinstallations.