Why Your Slip-On Needs a New Lock Nut and Header Bolts
By Yoshimura R&D of America, Inc. | Published: 2026-10-28
Category: Tips & Care
Learn why exhaust lock nuts and flanged header bolts loosen, how to spot wear, and when to replace them with genuine Yoshimura hardware.
Quick Answer
If your slip-on rattles or shifts at the mounting point, check the M6 nylon lock nut and flanged header bolts first. Replace them with fresh Yoshimura hardware when the nylon insert no longer grips or the bolt threads show wear.
Why Lock Nuts and Flanged Bolts Work Together
The M6 nylon lock nut is the small piece that keeps your exhaust mounting point from vibrating loose. The nylon insert creates friction on the threads, which resists the constant shaking from the engine and road. The 8mm flanged hex head bolt spreads the clamping load over a wider area than a standard washer, which helps prevent the bolt from digging into the mounting tab or the exhaust bracket.
When either part wears out, the other has to work harder. A lock nut that no longer grips lets the bolt turn freely, and a bolt with damaged threads can chew up the nut's nylon insert. That is why a loose slip-on is often a sign that both pieces need attention, not just one.
Diagnose the Loose Slip-On
- Symptom: The slip-on rattles, shifts, or rotates slightly at the mounting point, especially after a ride. A loose mount is not normal; address it before the exhaust hanger or bracket wears.
- Likely Cause: The M6 nylon lock nut has lost its grip because the nylon insert is worn or the bolt threads are damaged from vibration or over-torquing. Inspect both the nut and the bolt threads for wear before deciding what to replace.
- Corrective Action: Replace the M6 nylon lock nut and the 8mm flanged hex head bolt with fresh Yoshimura service parts. Torque the fastener to the specification in your exhaust manual, and re-check it after the first heat cycle. After replacement, verify the slip-on stays tight through a full ride and a re-torque check.
- Stop or Choose Another Option: If the mounting tab, bracket, or the slip-on itself is cracked or deformed, stop and replace the damaged component instead of forcing new hardware onto it. Hardware cannot fix structural damage; replace the part before reinstalling.
Hardware That Fits the Job
- M6 X 1.0 NYLON LOCK NUT: Genuine Yoshimura M6 x 1.0 nylon lock nut, sold as a replacement service part. Using the correct thread pitch and a fresh nylon insert ensures the nut holds its torque on the exhaust mount.
M6 X 1.0 NYLON LOCK NUT - 8mm X 50mm FLANGED HEX HEAD BOLT: Genuine Yoshimura 8mm x 50mm flanged hex head bolt, available as a replacement service part. The flanged head spreads the clamping force evenly, and the correct length keeps the bolt from bottoming out or protruding too far.
8mm X 50mm FLANGED HEX HEAD BOLT
