BMW R850 Maintenance Manual page 22

- turn both in, clockwise, to decrease the idle speed.
10. Adjust the same large brass bypass screw on each TB to get the Twin Max to
zero i.e. to balance the TB's at idle. You can turn just one of the screws for a
minor adjustment, or both screws in opposite directions if the balance if off quite
a bit. The screws should be within ~1/2 turn of each other when you are finished.
11. Shut the engine off and recheck that the Twin Max is still calibrated to zero.
12. Start the engine and double check the idle speed adjustment and balance.
"High" Speed Balance
Note: It used to be recommended to do this adjustment at ~3000 - 4000 rpm or
normal cruising rpm where surging would be most noticeable. However, Paul
Glaves points out that an adjustment at just off idle will be more accurate
because any difference between the throttle plates, left to right, will be a higher
percentage difference in the airflow and vacuum.
12. With the grip throttle, raise the rpm's to just off idle, ~1500 rpm.
13. The Twin Max needle should remain at zero, if not you will need to adjust the
right side throttle body cable.
14. Loosen the right TB cable locknut, located just to the left of the right TB,
using a 10mm wrench.
15. To get zero at off idle, turn the adjuster on the above cable as follows:
clockwise – moves the Twin Max needle left
counterclockwise – moves the Twin Max needle right
Note: Since the adjustment usually changes when you retighten the locknut, it
may be easiest to turn the adjuster a little in the correct direction eg. 1/8 turn, and
then tighten the locknut with the 10mm wrench while holding the adjuster with
needle nose pliers. Now look at the Twin Max to check your adjustment at off
idle. Keep repeating small changes of the adjuster and tightening the lock nut
until you have zero at off idle.
16. Turn the engine off and recheck that the Twin Max is still at the zero
calibration.
17. Start the engine and do a quick double check of the idle speed adjustment
and the off idle (high) speed adjustment.
18. Turn the engine off and remove the Twin Max hoses from the TB's.
19. Reconnect the vacuum hoses to the TB's.
Note: For more detailed instructions see pages 53 - 59.
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