BMW R850 Maintenance Manual page 63

part to tweak. These instructions assume that you know almost nothing about the bike,
where parts are located, or how it functions. The priority here is to help you diagnose
and adjust the bike, not engineering or theory. You may need detailed instructions the
first time you do the adjustment; subsequent adjustment will require much less
information. If you run into problems, contact the author by private eMail or at (305)255-
1010. For another perspective on setting the TPS, look at Rob Lentini's original work
which has already been cited.
III. How to set the TPS on the R850 and R1100
WARNING: BMW does not approve of this procedure. BMW warns that "The sealed
stop screws on the throttles must not be tampered with, or else the basic idle flow setting
will have to be reset by the manufacturer." There is a Throttle Position Sensor article by
Bob Gorman and an early Throttle Position Sensor article by Rob Lentini that present
ways to set the TPS without resetting the throttle stop screws. These do not violate the
BMW warning and these may be used before resorting to this procedure. The author of
this article assumes no liability for any damage or injury to you or your bike caused by
any errors or omissions.
Read through these instructions, and also "Throttle Body Balance for Dummies", before
you pick up a wrench or screwdriver. Find the parts before you start. This will save
work and cursing time.
Begin with a cold engine and do not start the engine until after the TPS has been
adjusted. Place bike on center stand with side stand retracted. You will need two
special tools, a digital volt meter (DVM) for setting the TPS, and a set of mercury
manometers (also called carb stix or mercury columns) for setting the throttle bodies.
12 Steps to Throttle Set Screw / TPS Adjustment
1. Loosen throttle cable (left side)
2. Loosen throttle body crossover synch cable (right side)
3. Back out the left throttle plate stop screw (underneath left side)
4. Attach DVM to red-white TPS wire #1 (rear) - ignition on
5. Move TPS to obtain zero reading (.006 volts) and lock TPS
6. Move left throttle plate stop screw to obtain .370 volts and lock screw
7. Large brass bypass screws in, bike on, warm engine, rough idle expected
8. Turn the large brass bypass screws out in 1/4 increments if bike will not idle; attach
carb stix
9. Set right throttle plate stop screw using carb stix
10 Reduce TPS in increments of 0.020 if idle exceeds 1100-1200 rpm
11. Reset throttle cable (left side) to .5 mm free play
12. Perform the "Throttle Body Synch for Dummies".
Each of the 12 steps above is explained below, with a detailed explanation of how to find
and adjust the correct part. All of the information on Step 1 will follow the Step 1
heading.
Step 1. Loosen throttle cable (left side)
Here are four (A-D) ways to find the throttle cable. Use all of these the first time you use
these instructions to ensure that you have the correct part.
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