Zero = Zero Throttle Position Sensor Tuning - BMW R850 Maintenance Manual

Super Tuning!
"Zero = Zero" Method for Adjusting BMW Oilhead Throttle
Position Sensor To Reduce or Eliminate Engine Surging - Rob
Lentini
Need:
Many BMW R259 "Oilhead" Boxers surge at constant throttle settings and low to
moderate speeds. Precise adjustment of the Throttle Position Sensor (TPS), one
of the two most important input sensors of the Motronic fuel injection system, is
critical in reducing or eliminating surging.
History:
Since 1994, BMW and dealer service personnel have not totally satisfied their
customers in solving this problem. At least one factory "service bulletin" has
addressed this issue with mixed results.
Caveat:
Performing the following procedure is not BMW approved and may void the
warranty if a failure has a "causal" relationship with this non-approved procedure.
Prerequisite:
Performer should be a reasonably skilled mechanic with knowledge of Motronic
fuel injection theory of operation. He/she needs a quality Digital Voltmeter, a
mercury or electronic manometer and common tools . All scheduled maintenance
should be performed prior to this procedure. Specifically, ignition timing, spark
plugs, valve clearances, Motronic coding plug and checking for throttle housing
inlet manifold air leaks should be performed per BMW procedures. On rare
occasions, the main electrical harness has also been at fault. ALL warranty
procedures should be requested, performed and documented on a warranty-
covered motorcycle prior to attempting this adjustment. The following should be
performed only after there is NO warranty recourse left or warranty in effect.
Doing this procedure could be at your own risk.
Note:
"Oilhead" BMW spark plugs are Bosch FR6DDC of dual "side electrode"
configuration. The author has found that standard "over the center electrode"
plugs, specifically Autolite 3923, contribute to smoother running and less surge.
Simply replacing the OEM Bosch plugs with the Autolite 3923 gapped to .028"
could solve some surging and obviate the need for TPS adjustment. Change
from non-BMW plugs at your own risk. And....
79