Valve Lash Increase; Results Of Increased Valve Lash And Advanced Timing - BMW R850 Maintenance Manual

- Notice on the lower (crankshaft) pulley that the three timing plate securing
screws are exposed, and that the timing plate (which the Hall transmitters are
mounted on) can slide CW and CCW in three slotted holes.
- Put the tranny in 5th gear and, while observing the flywheel with a good
flashlight, move the rear wheel to rotate the engine. You will be looking for "OT"
(top dead center), "Z" (full advance) and "S" (the 6 degree initial advance mark).
- Warm the engine and observe, with a timing light, where initial advance is
taking place. With the engine at 1000 RPM or less, the advance will be very
close to "S". Turn off the motor, loosen the three screws holding the Hall
transmitter plate, and tap the plate in a CCW direction from the front to the end of
slot travel. Tighten down the three screws and recheck the timing. Be SURE the
idle RPM is 1000 or less! If your R1100 is like mine, the timing will be advanced
50% further than the "OT" to "S" mark, for about 9 degrees of initial advance. If
so, put everything back together and, if during your test ride you detect no
noticeable detonation, you are in business. I recommend only Premium fuel if
the ignition is advanced. Never use less than the BMW-recommended Mid
grade fuel if the ignition is not advanced.
Valve Lash Increase - Rob Lentini
If you are like me, try this. I like low and mid-range driveability and throttle
response. My R1100RS would not idle for several minutes on cold mornings
until I increased valve lash. Increasing valve lash FIXED the problem, and I've
lost no discernible top-end power. Increased valve lash is equivalent to closing
the valves sooner--"milding" the cam timing.
Set the valves COLD from/to:
Intake:
Exhaust:
Your idle will be MUCH smoother and throttle response immediate but
controllable. Increase in valve noise is minimal. Valves will run cooler.
Results of Increased Valve Lash and Advanced Timing - Rob
Lentini
The following results were obtained from several runs on a dyno with my 1994
R1100RS:
1. Advanced timing (9 degrees) results in a 2 - 4 horsepower increase across
the entire RPM range. The 4 horsepower increase was in the meat of the power
band, from 6000 RPM and up. There was no detonation.
Spec: .006" to: .012"
Spec: .012" to: .014"
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