Milwaukee-Eight Common Issues by Model Year: What Owners Should Watch For

The Milwaukee-Eight launched in 2017 to replace the Twin Cam, and it's a genuinely more refined engine — better cooling, less vibration, and improved oil control. It's not, however, without its known issues. Here's what we watch for on M8s that come through our shop, by rough production era.

Early M8s (2017–2019)

• Cam chain tensioner wear — Less common and less severe than the Twin Cam issue, but early hydraulic tensioners on high-mileage examples still show wear. Worth a cam chest inspection past 100,000 km.
• Oil weep at the pushrod tubes — A minor, well-known cosmetic leak on some early production engines. Rarely serious, but easy to address during a rocker box service.
• Excessive heat at low speed on 114/117 CVO models — Riders in stop-and-go traffic sometimes notice more heat than expected; largely a characteristic of the larger displacement rather than a fault, though rear cylinder deactivation software updates helped later models.

Mid-Production (2020–2022)

• Clutch basket rattle at idle — A characteristic Harley wet-clutch noise that alarms new owners but is generally normal; worth confirming against a known-good example if it seems excessive.
• ECU/EFI sensor fault codes — Increasing use of factory-level diagnostics on these years means more sensors that can throw codes — most are cheap fixes (O2 sensors, TMAP) once properly diagnosed.

Recent Production (2023–present)

• Fewer widespread mechanical issues reported — this generation benefits from a mature platform with years of running changes already incorporated.
• Software and infotainment quirks — most reported issues on the newest bikes are related to the connected infotainment and rider aid systems rather than the engine itself.

Universal M8 Maintenance Items

Regardless of year, the M8 rewards consistent maintenance: three-fluid service on schedule, iridium plugs replaced at the recommended interval, and attention to the primary chain tensioner shoe, which wears on every Big Twin engine platform over enough miles.

The M8's biggest "issue" for us in Pictou County is honestly owner neglect during long winter storage, not the engine itself. A properly stored and serviced M8 is one of the most dependable Harley platforms ever built.

If your M8 is making a noise you haven't heard before or throwing a check-engine light, bring it in — factory-level diagnostics let us pull exact fault codes rather than guess.