I’ve been driving myself crazy trying to figure this one out. I have a 2023 CB650R. I recently installed a CS Racing full exhaust system. A buddy recorded a flyby of the bike and we noticed this “thumping” sound that becomes evident as the bike approaches redline. I recently had the ECU reflashed thinking perhaps the bike was somehow backfiring while under load. The problem persists and sounds no different post reflash. Any ideas? It sounds like a belt fed machine gun. The bike rides and operates flawlessly. I can’t hear or feel this thump while riding the bike.
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All 650Rs Thumping sound near redline under load
Any idea what rpm/speed that’s at? Sounds to me like it might be a soft rev limiter.
- Jul 5, 2020
Soft rev limiter? Meaning the bike isn't fully limiting but starting to as it approaches the actual rev limit? Or something else?
I've been following this guy on Reddit as well and noticed my bike making a similar noise. It's definitely at the top end of the RPM band, though, I haven't had a chance to ride the bike to find out at what point it specifically starts at. Sounds like some testing is in order.
Yep. I’ve no experience with the newer 650Rs so I’m not sure if they have one but I have seen/heard/experienced a soft limiter kick in before the real one kicks in. And this sounds like it.
- Jul 5, 2020
Good to know. Thanks for the input, even if anecdotal. I wasn't even aware that a limiter could operate in that fashion. I think it makes some sense though, sort of like hitting the brakes or pulling the clutch before an impact as opposed to just gassing all the way into it. Less velocity before a sudden change of force.