BMW R850 Maintenance Manual page 53

First attach the Carb-Stix to the each throttle body by removing the black
vacuum hose on the underside and attaching the Carb-Stix. It is not necessary to
plug off the removed vacuum hoses. If you have fuel injector covers on your bike
remove the right side cover only. We will perform the synching operation with the
bike running. It must be at normal operating temperature, but take care to not let
it overheat. If you cannot complete the operation in 5 minutes then let the bike
cool a bit and try again or use a fan to keep cool air flowing over the bike.
There are only two adjustments that can be performed on the R1100 throttles,
idle and throttle cable. The idle adjustment is accomplished by turning the brass
screw on each throttle body. They are big screws so you can't miss them. DO
NOT set the idle speed by manipulating the throttle stop screws like the older
twins. The starting point for the idle screw setting is 1 1/2 turns out for the RS
and RT and 2 turns out for the R and GS. Before setting the idle make sure you
loosen the right side throttle cable. There can not be any pull on either cable.
Start your bike and notice the mercury level rise in both columns. Take care
when dealing with mercury, it is extremely toxic. Turn each brass screw slightly in
or out to get the mercury levels dead even. The actual level is not important, we
just want both columns to be equal. When adjusted correctly the screws should
be within 1/2 turn of one another.
Now we'll go to the throttle cable. Only the right side is adjusted. The throttle
cable is a single cable that extends from the throttle grip to the left throttle body
and then continues over to the right throttle body. By manipulating only the right
side we are synching the right with the left. All we care about is that both throttle
bodies are pulling equal vacuum. With the bike running raise the rpms and watch
the mercury level rise. We want them to rise together and stay even at all rpms.
This is easier said than done. Don't worry too much if they are off slightly. Your
target point is just when all the slack is removed from the cable but before there
is so much tension that your idle is affected.
Make sure the columns are close at 4,000 rpms, the dreaded surging range.
Some tuners like to use the throttle lock to keep the rpms even but I prefer to
continue to raise and lower the rpms instead. Be careful not to chop the throttle
suddenly from high rpm's, as this can potentially suck mercury into the motor. If
you need to make an adjustment loosen, or slacken in BMWese, the 10mm lock
nut on the cable nipple. Turn the cable nipple in or out being careful not to turn
the cable housing at the same time. Keep checking to make sure the cable turns
freely in the nipple. Make small adjustments, 1/2 half turn in or out can make a
difference. Once you get the mercury columns to rise together and settle fairly
closely at various rpms you are done. Secure the lock nut and check one more
time.
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