Menu Close

Oil Filler and Cam Cover Leaks

Fixing Oil Filler and Cam Cover Leaks

by Stephen Karlan (Dali Meeow  –


Viton® O-Rings for all R850 and R1100 BMWs

If you own an R850 or R1100 BMW and there is excessive grime or some messy oil leaks around the oil filler cap or the black plastic cam covers at the rear of the cylinders, then your bike might benefit from some high temperature O-rings. The original O-rings are made of soft materials and will deform after extended use and heat.

The solution is two-fold. While you are changing O-rings, also check the plastic for any casting flash. This hint comes from Rob Lentini, who suggests that you run your fingers over the inside of the plastic parts and feel for bumps or rough spots created when the parts were made. Many plastic parts have this bump or ridge and, if it has not been smoothed, it provides a path for oil to leave the engine. Take fine wet-dry sandpaper or a fine file and smooth off any bumps.

Thanks to Bob Gorman ( for identifying the problem. He said, “For some reason BMW choose to use an O-ring made out of a very soft material. Over time this material will lose its ‘O’ and become flattened, allowing oil to easily flow around the seal.” Even the Viton® O-rings will wear over time, but that should be measured in years.

The second part of the solution is to replace the O-rings with a high temperature material called Viton®. These are made for aircraft and are used in extreme conditions — they work well in the BMW. There may be local sources for these Viton® O-rings in your area; check for a seals shop listing in the Yellow Pages. If you have trouble finding the O-rings, I will send you a set for $15.00 if you send me eMail saying that you want a set along with your name, full address and telephone number. Click on “send me O-rings” and make sure you include all of your mailing information and phone number.


Replacing the oil filler O-ring.

Do this with the engine cold. Locate the black plastic oil filler cap on the top of the left cylinder and remove it. Inspect the filler cap and check the O-ring on the bottom to be certain that it is soft and not damaged. Do not remove the O-ring on the inside of the filler cap, this is not the one you want to replace. Put the filler cap aside.

There is a black plastic ring still in the cylinder head. Locate the black tab at the rear of the ring that mates with a small depression in the cylinder head; observe this tab because you must line up the tab when you reinstall the plastic ring later. The O-ring that you want to replace is located on the outside edge of this black plastic ring; this O-ring is the only thing holding the black plastic ring in place. Remove the black plastic ring carefully by placing your pinky finger in the oil filler hole and pulling up gently or by prying it out (try a flat-head screwdriver). When it is out, use your fingers or a small flat-head screwdriver to remove the old O-ring on the outside of the plastic ring, check the plastic, and install the smallest of the Viton (R) O-rings from the set of three that you will need for this installation.

Reinserting the black plastic ring can be tricky. It is a tight fit and you do not want to crack it. Lubricate (with oil) the part and line it up (black tab) and try to push it in by hand. Repeat several times. If that does not work, install the oil filler cap back into the black plastic ring (both plastic pieces now mated) and align the black tab on the ring with the cylinder depression. Lubricate and tap gently. If you tap too lightly, nothing will happen and you will have to tap again slightly harder. If you tap too hard, you may crack the plastic ring. You are better off tapping too gently and then trying it a second or third time. In other words, be careful. Total time: five minutes.

Replacing the cam cover O-rings.

Do this with the engine cold. On the R1100RT, the side fairings must be removed. On the R, RS and GS, nothing must be removed. Locate one of the Cam Cover O-rings on the back surface of the cylinder head. It is a black, oblong piece of plastic located 5.5-in. down from the top and 4.5-in. in from the side of the cylinder head. It is located low on the back surface of the cylinder head, below the large black fuel intake tube. The Cam Cover is held in place with two allen-head screws that measure exactly 2-in. from the center of one to the center of the other. Remove the allen-head screws and, using a small flat-head screwdriver or other similar tool, pry the black cover away from the cylinder. It should come out easily. Use the same small flat-head screwdriver to gently pry the O-ring out of its channel in the black cover. Check the black cover for casting flash & smooth out with steel wool or small file. Install the new Viton (R) O-ring by hand. With the new O-ring in place, position the cover over the hole and install the allen screws by hand. Check the alignment and then tighten the allen screws alternately a few turns at a time so that the cover seats itself in the hole evenly. Do not over torque; the allen screws are going into aluminum !! Total time: Four minutes each side.

Plan to install these the same day you get them, it is that fast and easy. All tips or corrections to the instructions are welcome. Let me know if you find any damage to the O-rings you are removing so that I can update my data base.

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.

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

Leave a Reply