BMW R850 Maintenance Manual page 66

remove the hose if necessary. Remove (cut off) the plastic cable tie that secures a wire if
it obstructs the working area. Replace the cable tie, hose and clamp when finished with
the throttle plate screw adjustment. The physical manipulation that is described in the
next paragraph (especially on RS models) is a challenge to your stamina and will take
time, patience and any odd-ball tool that works. If you find a tool that makes this easy,
please please please contact this author with your hint.
Your job is to loosen the 10 mm lock nut (counterclockwise) using a small wrench, and
then loosen the 8 mm stop screw (counterclockwise) using a wrench or a screwdriver so
that the metal flange piece does not contact the screw at all. If you loosen the screw a
few turns you should be able to see a gap between the end of the screw and the metal
flange piece. You must see a gap, which means the left throttle is closed. There must
be a gap !
Step 4. Attach DVM to red-white TPS wire #1 (rear) - ignition on
The TPS is mounted on the outside of the left 2 1/4 inch metal tube you have been
working around; it is a black flat plastic cover that measures 2 1/2 inches wide x 2 inches
high with the word Bosch imprinted on it. This cover is attached by two allen-head
screws through the cover and the allen-head screws describe a horizontal line.
There is a prong attached to the bottom of the TPS, and a rubber boot that covers the
bottom of this prong. The prong can be removed easily by depressing the wire, which
acts like a latch, and pulling down. Do not remove the prong. Nothing bad will occur if
you do remove the prong from the body of the TPS, but for this adjustment the prong
must be attached.
The rubber boot that surrounds and protects the wiring that enters the bottom of the TPS
must be moved out of the way. Exert only enough force on the rubber boot to wiggle it
down far enough to expose about 1/2 inch of the four wires that enter the prong. The
wire furthest to the rear is coded; it is white and red and called wire #1. Insert a sewing
needle, a paper clip or other sharp and thin metal (electrical conducting) object up and
into the plastic housing where the white and red wire enters the prong.
Step 5. Move TPS to obtain zero reading (.006 volts) and lock TPS
Attach the ground probe (lead) of your digital volt meter (DVM ) to the spring of the side
stand or some other grounded metal object. Attach the other probe (lead) to the object
inserted into the white and red wire. With the bike on the center stand, with side stand
retracted, and with engine cut-off switch on the right handle bar indicating "on", turn the
ignition key to "on" but DO NOT start the bike.
Read the DVM and record this TPS value for possible future reference. Do not remove
the TPS screws; loosen them so that the TPS can be moved (adjusted). Turning the
TPS slightly in one direction will increase the voltage; turning it in the other direction will
decrease the voltage. Turn the TPS until the observed voltage decreases to about .006
or .005 volts, which probably is as low as the voltage will go. If it will go no lower, that's
okay. DO NOT continue to turn the TPS after it reaches its minimum value, which is
close to zero. Start at a high value (.300) and turn the TPS until it reaches the low value
(.006 or .005) and stop. [Note: Some digital voltmeters have an autorange function;
below a certain value they will read in millivolts. The .006 may read as 6 MV, which is
the same as .006 volts. Don't let the decimal places confuse you.]
Stop moving the TPS just when the voltage stops decreasing and lock it down there. At
this point we say the TPS is at zero. The throttle position is also at zero. The TPS is
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