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R1200RT backfiring


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Could just be a change of earplugs making me aware, but I wonder whether the bike has a problem, and if so what might be causing it.


Noticed on ride today that on over-run, there is sometimes a gentle backfiring. Not a percussive noise, just a pop-pop-pop from the muffler.


Bike has nearly 8k on the clock, was serviced at 6k. Only recent work done on the bike was having a corroded timing cover replaced. I don't know if this job involved removing the timing chain and replacing it, hence an associated risk of getting one cog out on reassembly.


Last 2 visits to the dealer, his monkey overfilled the oil, and I had to remove a third of a litre each occason get level down to be visible in the sight glass. So the bike may have been run for a few hundred miles overfilled, just possible the engine sooted up a bit. Although I would have thought that vigorous riding since would have blasted that clean.


Bike seems to be performing fine otherwise.


Ambient temperature today quite high for a UK springtime, at 21 deg C, or 70 deg F.


Or it may be that all 1200s do it, and I just haven't heard the noise before.


I guess that if it is actually a problem, paranoia suggests that there's some risk of cat damage.


Comments/thoughts/suggestions will be much appreciated.

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Sounds like a normal pop-pop-pop associated with a lean condition on decel.


Wouldn't worry about it.


If it is truly bugging you then I would do a cursory check to make sure the intake tract is snug, the header bolts are snug and there is no evidence of blow by, and then ensure your muffler is snug at the attachment point to the header. Lastly, double check to ensure your O2 sensors are snug.


Hope this helps.

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My ST's done that since new. Just a light popping that I can hear usually at low speeds. Since the 7 series update was done it is not as loud and less of it. I'd say it's pretty normal.



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The popping is by design. An emissions control device, usually called PAIR (Pulsed Air Inject R-something or other) valve, injects fresh air into the exhaust gases at just the right time so as to cause any unburned fuel present in the exhaust gases to burn. This produces the popping and burbling sound you hear, this typically only happens as you decelerate. Many people remove or disable the PAIR valve when the switch from stock to straight or other custom pipes as the popping can be quite loud without a muffler however to do so would probably cause your vehicle to fail an emissions test, if one was required for it.

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Don't think there is any such device on the BMW. I do have Pair valves on my XX but the factory map is so rich that it is a non-issue. The pair valves will confuse an exhaust gas analyzer though so it is a good idea to disable them for performance tuning on a dyno.

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The issue of backfiring came up when the 1200RT started production. My dealer received a tech note from BMW stating that it was normal, and usually occurs when decelerating with the throttle partially open. On mine, I just close the throttle completely and backfiring stops.

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