How to Install a Full Exhaust on a Honda Grom
By Yoshimura R&D of America, Inc. | Published: 2026-10-20
Category: How-to Guides
Step-by-step guide to installing a Yoshimura RS-9T full exhaust on your Honda Grom. Includes tools, common mistakes, and fitment tips.
Quick Answer
Installing a full exhaust on a Honda Grom is a straightforward job that takes about an hour with basic hand tools. The Yoshimura RS-9T high mount system is a popular choice for its power gains and clean look.
What You'll Need Before Starting
A full exhaust swap on a Grom requires basic metric sockets (8mm, 10mm, 12mm), a torque wrench, penetrating oil for stubborn bolts, and a new exhaust gasket. The Yoshimura RS-9T kit includes all necessary hardware except the gasket and O2 sensor plug if your model uses one.
Work on a cold engine. The exhaust bolts can be tight, especially on a bike that has seen some miles. Apply penetrating oil to the header nuts and muffler hanger bolts 15 minutes before you start.
Common Challenges with the Grom Exhaust
The stock exhaust on the Grom is compact but the nuts can corrode. The O2 sensor (if equipped) may be seized. The RS-9T high mount system uses a different hanger location than the stock low mount, so check clearance to the rear shock and turn signals before tightening everything.
Installation Steps
- Remove the stock exhaust: Loosen the two header nuts at the cylinder head using a 10mm socket. Remove the muffler hanger bolt (12mm) near the passenger peg. Slide the stock system off the head studs and out from under the bike. Watch the exhaust gasket – it often sticks to the head. Common mistake: Forgetting to replace the exhaust gasket. Always install a new one to prevent leaks.
- Install the new header and muffler: Place the new exhaust gasket onto the head studs. Slide the RS-9T header over the studs and hand-tighten the nuts. Mount the muffler to the high mount bracket using the supplied hardware, but do not fully tighten yet – leave everything loose for alignment. Checkpoint: Ensure the muffler clears the rear shock and turn signal. Adjust the hanger position before tightening.
- Tighten and torque all fasteners: Starting from the header, torque the header nuts to 18 ft-lbs. Then tighten the muffler hanger bolt to 15 ft-lbs. Finally, tighten the mid-pipe clamp if included. Reinstall the O2 sensor if your bike has one, using anti-seize on the threads. Common mistake: Over-torquing the header nuts can strip the studs. Use a torque wrench and follow the spec.
- Check for leaks and test ride: Start the engine and let it idle. Listen for exhaust ticks at the header joint. Spray soapy water around the gasket area – bubbles indicate a leak. If everything is tight, take a short ride, then re-check all bolts after the system has heat-cycled once. Checkpoint: Re-torque the header nuts after the first heat cycle – they can loosen as the gasket compresses.
Product Used in This Guide
- GROM 2022-26 RS-9T Stainless High Mount Full Exhaust, w/ Stainless Muffler: The RS-9T Speed Series High Mount system includes an 18mm Wide Band O2 sensor bung for tuning and is optimized for the latest gen Honda Grom. The O2 bung lets you install a wideband sensor for fuel tuning, which is important to get the full performance benefit from the exhaust.
GROM 2022-26 RS-9T Stainless High Mount Full Exhaust, w/ Stainless Muffler
