Exhausts and Engine » Question for those with aftermarket exhausts

Hello everyone, I have a follow up question related to a recent post in the "Leo Vince exhaust on a 1250RS - It fits!" thread. As described there, I recently installed a Leo Vince Euro 4 version originally designed for the 2017-18 R1200 motor.

Has anyone else with a less restrictive aftermarket exhaust on their 1250 noticed a distinct 'pop' during moderate to heavy acceleration through 4000rpm in the lower gears? It's loud enough to grab my attention every time (with or without earplugs) and distracts me from an otherwise enjoyable audible soundtrack. My assumption has been that it is the shift cam switching lobes and nothing to worry about. I re-installed the OEM can and no longer hear it, so perhaps it is masked by the more circuitous design of the larger, heavier can? If so, then the newer offerings for the 1250 engines by Leo Vince, Remus and Akropovic (similar in appearance to OEM) may be the better choice for these bikes.

Now I am debating whether the better sound, better looks, and lighter weight of this aftermarket exhaust outweighs the annoying popping noise during acceleration. Anyone else's experiences would be appreciated!

Are you considering an ECM tune now that you've modified your exhaust? The ECM's self-adjusting fuel-air mixture can only compensate so far, often requiring a tune to address extra pops and bangs.

The Leo Vince on my 1200 is fine going up the the rev range, just pops a bit on the over run.

If it turns out to be a tuning issue then I'll probably stick with the OEM can, as I assume a custom tune would be costly and void the warranty. When I was initially considering the Leo Vince purchase the local BMW tech advised that installing an r1200 exhaust shouldn't pose a problem. I haven't yet discussed this popping issue with him.

Personally I think the motors make this noise as standard anyway, only it's lost in the GIANT END CAN-an-an-an-an.

The popping you describe sounds like what you get when using the quickshifter. It's there with the OEM can but I found it more noticeable with an approved aftermarket can on my 1200. It's almost certainly not related to the shift cam. If your 1250 was Euro 5 you have downgraded the motorcycle by fitting a Euro 4 can.

I fitted an Arrow can on my 1250RS and it does the exact same thing as yours. I too, believe it’s when the cam shifts around 4k rpm. It is a bit distracting but a small trade off for the sweet sounds otherwise.

Don’t know if a tune would remove this particular pop, it may be a “feature” of the shift cam motor

WillC, thanks for the reply. I'm glad to hear someone else who has experienced this. Those who have not heard this understandably suggest it is the quick shifter or flapper valve, but it does not happen during shifts and the flapper valve is already full open at this point in the rev range.

Assuming it is the shift cam, I'm left wondering why it is more noticeable with the aftermarket exhausts? Seems like the mechanical 'clunk' of the cam shaft shifting over should be even more noticeable with the quieter OEM can. Unless the sudden change in valve timing somehow translates to an exhaust 'burp' out the less restrictive tailpipe.

I mistakenly thought the shift cam operated at 5k rpm and above but this document shows that the high loads cam can operate from much lower revs depending on load. So i take back what i said it could well be shift cam switching profiles.

https://sci-hub.se/https://doi.org/10.1007/s38313-019-0006-3

Zitat von Bunter im Beitrag #9

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I mistakenly thought the shift cam operated at 5k rpm and above but this document shows that the high loads cam can operate from much lower revs depending on load. So i take back what i said it could well be shift cam switching profiles.

https://sci-hub.se/https://doi.org/10.1007/s38313-019-0006-3

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Zitat von Bunter im Beitrag #9

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I mistakenly thought the shift cam operated at 5k rpm and above but this document shows that the high loads cam can operate from much lower revs depending on load. So i take back what i said it could well be shift cam switching profiles.

https://sci-hub.se/https://doi.org/10.1007/s38313-019-0006-3

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Zitat von Crawdad im Beitrag #8

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Assuming it is the shift cam, I'm left wondering why it is more noticeable with the aftermarket exhausts? Seems like the mechanical 'clunk' of the cam shaft shifting over should be even more noticeable with the quieter OEM can.

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Zitat von Freddyfruitbat im Beitrag #12

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Zitat von Crawdad im Beitrag #8

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Assuming it is the shift cam, I'm left wondering why it is more noticeable with the aftermarket exhausts? Seems like the mechanical 'clunk' of the cam shaft shifting over should be even more noticeable with the quieter OEM can.

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I have yet to swing my leg over a 1250, but everything I've ever read, or heard from other riders, suggests that it's impossible to detect when the shiftcam does its thing?

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Sometimes you can hear it in the engine noise. It becomes more rough sounding, just a bit more hoarse.

Zitat von Bunter im Beitrag #6

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The popping you describe sounds like what you get when using the quickshifter. It's there with the OEM can but I found it more noticeable with an approved aftermarket can on my 1200. It's almost certainly not related to the shift cam. If your 1250 was Euro 5 you have downgraded the motorcycle by fitting a Euro 4 can.

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