Oilhead Tech Pages


Adjusting Valves and Rocker Arms

Stephen Karlan (Dali Meeow)  -  dalimeeow@adelphia.net


Written for 1994 through 1998 - R850 & R1100 BMWs

TOOLS NEEDED

newspaper (oil catcher)
maglightdrip pan
med. screwdriver (pry)
3, 4, 5, 6 mm T handle Allen   
plug tool
compressed air
5/8-in socket and bar
2 sets gauges
hemostat for rubber cover       
10mm box wrench           
long screwdriver
5/8-in. or 17mm socket       
pliers
torque wrench

Start with a cold engine. Place bike on center stand and put newspaper under the cylinder heads to catch the oil drips.

Step One: Remove the black plastic alternator cover at the front of the engine using a 4mm Allen wrench. This black cover is behind the front shock and, after the Allen screws are removed, jiggle the cover and let it drop past the exhaust headers to free it. With the cover off, the alternator belt is visible. Check the tension of the alternator belt; it should move only slightly with thumb pressure. Leave the alternator cover off.

Step Two: Move to the cylinders, those silver jugs that jut out the sides of the engine. Remove the black plastic strip ["4 Valve" imprinted on part] by hand; this plastic part covers the spark plug area.

Step Three: Remove plug wire from the plug by using the 2-inch long black plastic loop tool supplied in the bike's took kit. The plastic loop tool acts a handle for removing the plug wire from the end of the plug. Holding onto the loop end, point the open side of this 2-inch plastic tool toward the rear of bike while hooking the tool onto the plug wire boot. Pull on the tool to remove the plug wire.

Use compressed air to blow out plug hole before removing the plug. Some camera shops might sell expensive compressed air used in cleaning lenses; this is over kill. If you don't have a compressor, use a straw or small flexible plastic hole and blow. There will be stuff in that hole that you don't want in your cylinder ! You'll need lots of lung power here.

Step Four: Remove the spark plug using the deep socket supplied in the tool kit.

Step Five: Place a pan or some newspaper under the valve cover to catch the small amount of oil that will drip when you loosen the four valve Allen screws that secure the valve cover. Loosen the four Allen screws with a 6mm wrench and remove the valve cover; tap lightly if it's stuck.

Rotating Engine Cylinders

Step Six: The reason for rotating the engine cylinders or flywheel is that, as you do this, the valves will move and you can position them for the adjustment phase. You must use one of two means to rotate the engine cylinders. Option one is recommended and it is easy for one person to perform the adjustment.

Option One: Return to the alernator area and locate the 5/8-in. or 17mm nut (depending on bike) which is the lower alternator drive pully. Place a socket on the nut to turn the lower alternator drive pulley (and engine) clockwise. As you turn the alternator drive pully, the cylinders (and valves) will move.

Option Two: This method requires that two persons work together. Put the bike in gear and, with the bike on the center stand, carefully rotate the rear wheel to move the cylinders the valves (but not the bike).

Positioning the Cylinders

Step Seven: Now that you can move the cylinders (and the valves) you will want to position the valves for adjustment. There are three ways to do this.

Method one: Remove both spark plugs and place a long screwdrive in the cylinder next to the first set of valves you are going to adjust. You can adjust the left or right side valves first; it makes no difference. Place the screwdriver tight against the piston crown. [ Do not use a wood pencil, Chinese chop stick or soft wood object because a piece could break off inside the cylinder. Removing the piece could be complicated and expensive.] Rotate the alternator nut clockwise or the rear wheel until the screwdriver projects the maximum distance out of the cylinder. When the screwdriver is at maximum extension, check the valves on both left and right side -- adjust the valves on the side where the adjustment gap "wiggles". Step Eight will explain how to adjust the valves. After you adjust the valves on one side, it is a good time to perform the rocker arm adjustment; see the directions near the end of this article for that information. After adjust the valves on one side, move the engine 360 degrees by rotation the alternator bolt or the rear wheel, and adjust the valves on the other side of the engine.

Method Two: Instead of using the screwdriver in the cylinder, you may remove the round black rubber timing hole cover (size of quarter) located on right side of engine (above and to the rear of the cylinder head, below ABS wiring, over the flywheel) by grabbing the edge of the cover with a hemostat (medical tweezers, needle-nose pliers) and pulling. Timing marks will be seen inside of this hole.

If you are going to position a cylinder by using the flywheel marks, you need a flash light (small Maglight or flexible stalk flashlight) to illuminate the flywheel marks inside the timing hole. The marks,in the order in which you will see them inside the hold and on the side of the flywheel,are "Z", "S" and "OT". You want to center the "OT" mark in the opening. If you position the cylinder in this manner, you may check your work by inserting a screwdriver as explained in Option 1.

Be careful when reinstalling the small rubber cover that you do not push it all the way through, into the hole. When reinstalling the timing hole cover, especially on RT models where it is extremely difficult to reinstall, use a needle and heavy thread to sew a loop in the cover so that you can retrieve the cover if you push it into the hole. Place the loop in the cover so that, when the cover is in place, you can pull one end of the thread to remove it from the cover. If you damage or destroy this timing hole cover, clean the hole area with gasoline and cover it with duct tape while the dealer obtains a new one for you.

There is an optional method that I will designate Method Three for moving the cylinders into place. This is not recommended and is presented only to be complete. Put your finger over the spark plug hole and feel for air pressure; when the pressure stops, the piston is at maximum extension (the top of its stroke) and the valves are in position for adjustment. When used in conjunction with the flywheel marks, this will work. I have never been able to feel the air pressure at the spark plug hole because the hole is too recessed.

Adjusting the Gap

Step Eight: Adjust the valves using a 10mm box wrench, 3mm Allen wrench, two feeler gauges and a small torque wrench. A torque value of only 6 ft./lbs. must be observed because overtightening will damage the threaded adjuster.

BMW recommends the following two feeler gauge dance step. One gauge is used to adjust the intake (or exhaust) valve while the second feeler gauge is positioned under the adjoining intake (or exhaust) valve to stabilize and prevent the rocker from canting.

After the first valve is adjusted, stabilize it and adjust the second valve. To ensure that a valve is properly adjusted, attempt to insert the next thicker size of feeler gauge -- the feeler gauge should be too thick to fit into the gap. The valve clearance may change slightly as you tighten the lock nut. Experiment with tightening technique to maintain the gap as you tighten, and recheck the gaps after all four valves on one side of the bike have been adjusted. (The terms clearance and gap are synonymous.)

Optional three-gauge method to check valve clearance. For the exhaust, use three gauges sized 0.011, 0.012 and 0.013 inches. Use a 0.012 for stabilization of the valve adjoining the one being adjusted. On the valve being adjusted, the 0.011 should pass with no drag. The 0.012 should have a "light drag" and the 0.013 should not pass. This helps develop a feel for the desired "light drag". It cross checks the adjustment. (Submitted by Brian Curry in Chester Springs, PA bmwbrian@voicenet.com).

I own a special set of feeler gauges on which each gauge has two thicknesses. The 3/4-inches at the tip of the gauge will be 0.012 inches, the gauge then increases in size to 0.013 inches. When using these gauges, the 0.012-inch feeler gauge should fit with some drag (GO), but the 0.013 part of the gauge should not pass (NO GO).

The two exhaust valves are located nearest to the exhaust pipe. Adjust exhaust = .012 inches (.30 mm). If you err in adjusting the exhaust valves, err on the loose side. It is important that you do not adjust the exhaust valves tighter or smaller than 0.012 inches (.30 mm). Adjust intake = .006 inches (.15mm).

Adjust both the intake and exhaust valves on one side of the engine. Then adjust the rocker arm on the same side of the engine if you're going to do that. Only then should you rotate the engine 360 degrees and adjust valves on the other side of the engine.

Rocker Arm Adjustment

Mick McKinnon <bmwmick@comcast.net> points out that there is one additional gap to check while the valve covers are off. The rocker arms, which are the vertical metal pieces that contain the valve adjustment nuts, will move up or down when pushed by hand. Measure the two gaps where the rocker arms contact the horizontal piece at the bottom. This horizontal piece has several names, including lower rocker arm bearing carrier (LRABC) and rocker arm end plate. This lower rocker arm bearing carrier is held in place by three T45 torx screws in a triangle pattern (on its side) and one large head bolt. The gap between the rocker arm and the LRABC should be between .05mm and .30mm. The smaller the gap the quieter the engine. To adjust the gap, loosen the 3 Torx screws and, after marking the lower head bolt, loosen it also. Snug them back up just enough to hold an adjustment and then tap the LRABC until you have about .05mm end play (gap). Check the gap after tightening because it may tighten up slightly as you torque the screws and bolts back to spec. Retorque the T45 torx screws to 15 ft.lbs. Retorque the head bolt to 17 ft.lbs. and then turn the bolt an additional 180-degrees (torque it and then move the wrench through another half circle).

While the valve cover is off, torque the M10 head bolts (10mm diameter) to 29.5 ft.lb. (40nm). The M6 bolts (6mm diameter) that surround the cylinder housing should be toqued to 6.5 ft.lb. (9nm).

Clean valve covers and reinstall. Note that there also is a rubber block affixed to the lower front area of the engine that is visible when the valve cover is removed; align this block when reinstalling the valve cover. The valve cover must be free of all oil film or it won't seal. Be certain the center gasket at the spark plug hole is in place ! Reinstall plug, plug wire and valve cover strip.

Order of work: In tuning up the engine, adjust the valves first because the engine must be cold. If your bike is experiencing surging, perform a TPS and throttle screw adjustment (Zero = Zero) at this point. Read the first few paragraphs of the TPS article to see the difference between vibration and surging and to help you decide if you need to perform this adjustment. After all valve work and TPS adjustment, warm up the engine before performing fluid changes. The last stop is to perform the throttle body balance (fuel injection equivalent to a carb synch) with the engine running and a fan to cool the engine. The articles in order are:
  1. Adjusting Valves and Rocker Arms
  2. Setting Throttle Position Sensor and Throttle Screws
  3. Balancing Throttle Bodies


Torque data and clearances:

Spark Plug                      20 NM        15 ft.lb.
Valve adjust lock nuts      8 NM           6 ft.lb.
Valve cover screws         8 NM           6 ft.lb.
M10 bolts (10 mm)        40 NM         29.5 ft.lb.
M6 bolts (6 mm)             9 NM          6.5 ft.lb.
T 45                              20 NM         15 ft.lb.
Head bolts                     23 NM         17 ft.lb. + 180 degrees

Exhaust Valves            .30 mm     .012 in.
Intake Valves               .15 mm     .006 in.


The author has done his best to produce accurate information. However no responsibility can be accepted for any damage or injury caused by any errors or omissions in this article. Make certain that you understand what is described and why it is being done. Use at your own risk.

Updated 2002 for clarity, all clearances have remained the same. Rob Lentini, an experienced and superb mechanic and engineer, has some different clearances and procedures to obtain more low-end torque and engine characteristics which he enjoys. The values presented here are factory settings.

Comments, corrections and questions may be directed to
Stephen Karlan (Dali Meeow) at (305) 255-1010
or via email at dalimeeow@adelphia.net.
Updated November 23, 2004.


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Last Update: 09 September 2010