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Occasional 'mini-explosive sound' when blipping/rev matching on downshift


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This sound is followed by engine not delivering power (clutched pulled in, meaning engine's rpm doesnt rise) until I blip/twist the throttle again ; if i tried to replicate the sound by blipping numerous times again, i doesnt happen and engine runs and blips like normal.

It happens infrequently and randomly when I rev the engine with clutch pulled in; happens on both my brand-new Kawai vulcan 650 AND '16 CB125f (occurs more on the vulcan but could be coincidental that I just happen to rev match downshift more on the vulcan). Sound also seems to occur only when throttle is blipped fast (like a quick blip to downshift)

*sound also seems to be coming from the engine, not exhaust

I have no idea what it is and whether i signals engine damage?

Edited by potatobroxd
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Is it not just the exhaust popping on the over run? My ninja pops and bangs like a goodun :mrgreen:


Both exhausts are stock and I'm confident the sounds coming from the engine :s


Unburnt fuel in the exhaust? Or maybe just a blip.


I'm not sure but sound seems to be coming from the engine. The sound occurs more often (or only when, not sure) when I blip the throttle fast enough

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Normal for stock euro4 bikes. Nothing to worry about.

My 2018 Africa twin does it and makes me feel like a hooligan. It's a constant subject on the AT forum, they all do it.

For the older bike it's likely a small leak in the exhaust, probably and again, nothing to worry about.

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could be the secondary air system

Suzuki call it a PAIR valve but they are all the same



Thanks for that; that's answered a lot of questions about my Honda which also as a pair valve. :thumb:

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My ER5 pops and bangs on the overrun like a firework display because I've got an open can and no carb modifications. However, since I fitted my "New" engine the popping and banging is considerably reduced and I'm using the same carbs and pipe . I can only conclude that the fact that this engine has better compression and freshly lapped valves means that it burns fuel a bit more efficiently. Still sounds nice though.

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