BMW R850 Maintenance Manual page 34

Check Battery: Inspect the battery to ensure that the electrolyte level is between the
minimum and maximum marks. Top off to the maximum mark with distilled water.
Check the connections for signs of corrosion. Clean the terminals and connections as
required.
Check and Adjust the Alternator Drive Poly Belt: The alternator drive belt is located
behind the front cover. The alternator is mounted so that it can slide vertically up or
down when the retaining bolts are loosened. The lower retaining bolt on the left side
(your right as you are facing the front of the engine) contains a geared adjuster. The
adjustment specifications call for loosening the retaining bolts. Then tighten the geared
adjuster using a torque wrench to 70 inch lbs = 5.9 foot pounds = 8 newton meters. This
rotation raises the alternator and this properly tensions the belt. Tighten the other
retaining bolts to hold the alternator in place with the proper belt tension. To check the
tension of the belt without disturbing it, grasp one side of the belt midway between the
pulleys and twist it 90 degrees. If it will twist much over 90 degrees it is too loose. If you
cannot cause it to twist 90 degrees it is too tight. If the belt is too tight it places undue
stress on the alternator bearings. If it is too loose it will squeal. Please note that the
belts now in use by BMW will slightly squeal for a few seconds when the engine is
started cold. This is normal. Do not attempt to make the belt so tight as to eliminate this
cold start-up squeal. It will then be too tight.
Check the Spark Plugs: The spark plugs should be visually examined each Minor
Service. You should not expect to need to replace them at this interval however. The
early R1100's used spark plugs with three side electrodes. The current specification is
for spark plugs with two side electrodes. Examine the electrodes for signs of wear and
examine the insulator color. You are looking to find a very light tan insulator. A bright
white with blisters would indicate a lean mixture or other cause of overheating. Consult
any good motorcycle or car repair manual for the color spark plug pictures which show a
number of fuel fouled, oil fouled, lead fouled, and other abnormal conditions. Apply a
light coating of anti-seize to the threads when installing the spark plugs. Be careful not
to get any anti-seize on either the electrodes or the insulator. The torque specification
for the spark plugs is 15 ft. lbs (20nm).
Check the Brake Pads: Remove the brake caliper covers (lightly spread the cover
using a small pry bar or screw driver and lift upward). Carefully examine the brake pads
for wear. Do NOT assume since you brake properly as taught by the MSF and mostly
use your front brakes - that the rear pads do not need to be checked. The R1100
motorcycles consume rear brake pads at a relatively short interval. Examine them each
service, and expect to need to replace them every 20,000 to 30,000 miles. I know of
cases where the pad was gone and the backing plate scored the disk in 12,000 miles.
I've also seen them last 35,000 miles, but not a lot more. Even with proper braking
technique the front pads are likely to outlast the rear pads 2 to 1. The minimum lining
thickness is specified as 1.5mm (.06")
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