Service Bulletin #2851 reminds us of what the small print in our bike's documentation has always said: Deviate from BMW-approved procedures or parts at your own risk. You may void your warranty if the claim can be directly connected to unapproved modifications or non-standard parts. A manufacturer has the right to enforce this through "causal" effects as SB #2851 notes. Conversely, use of Autolite spark plugs can't be linked to a transmission failure, for example.
I understand and respect the homologation rules required by BMW and other manufacturers to sell their products in the US and other countries. To comply with smog/noise requirements may result in compromises in performance to meet federal and state statutes. It's a tough game, regardless of the best electronic engine management. I'm not knowledgeable enough to comment on "millions of test miles" that may or may not have been accomplished, in part at least, in the US by US riders.
My articles on careful throttle body synchronization, "Zero=Zero", spark
plugs and others were meant to improve the driveability and performance of BMW Oilheads
from the perspective of their owners. I stated in the "Zero=Zero" piece to NOT
perform this procedure if your machine was running satisfactorily. I meant that! "If
it ain't broke, don't fix it" makes a lot of sense. I implied that if you did this,
you are in some ways "on your own." I generally prefaced my comments to
recommending that their dealer inspect and correct any discrepancies found in the their bike, paying particular attention to possible Motronic faults set in the memory.
Unfortunately, some (very few) of you have communicated problems with doing procedures
I wrote up. In most cases, I determined that my instructions were misunderstood, not
completely followed, or the performer was, perhaps, less than qualified to be wrenching on
a sophisticated fuel injected motorcycle. This may have lead to some damage in certain
Many others are pretty darn well pleased with the results!
Here's the bottom line (from a non-lawyer!):
While I don't think that BMW has solved or has even totally acknowledged Oilhead
surging problems, be aware that if you tamper with paint-sealed adjustments, install
non-OEM sparkplugs, replace cat code plugs, intake tubes or perform other modifications,
you must accept the possibility of a "causal" warranty refusal if a claim you
make is proven to be related to
what you did to your bike.
Your warranty is a limitation on your modification of the motorcycle and a commitment
on your part to accomplish certain maintenance. But, it is also a protection to _you_ the
consumer by the manufacturer. You can modify original specification components/adjustments
at your own risk or after the machine is three years old or not covered by federal/local
regulations. Until that time, you can exercise your rights and insist on good driveability from your BMW if it is not performing as you would reasonably expect a ~$16,000 investment to function.