Adjusting the Valves on a BMW R1100S

Based on the original guide by Colt Self. Reproduced and edited for clarity with permission.

Valve adjustment on the R1100S is not difficult, but it rewards patience, accuracy and a calm approach.

This is standard Oilhead maintenance, normally carried out at 6,000-mile / 10,000 km intervals. A few hundred kilometres over that interval during a trip is not a concern. Just do the work when you are home again.

The engine must be cold. BMW specifies valve clearance at a maximum engine temperature of 35°C / 95°F; Colt’s “under 100°F” rule is therefore exactly right.

Specifications

BMW’s workshop data confirms 0.15 mm inlet and 0.30 mm exhaust clearance, measured cold.

Spark Plugs

Replace spark plugs every 20,000 km / 12,000 miles.

For single-spark R1100S models, BMW specifies the NGK BKR7EKC primary plug.

For twin-spark models, BMW specifies:

• Primary plug: NGK BKR7EKC
• Secondary plug: NGK DCPR8EKC or Bosch YR6LDE

Before You Start

You will need:

• Feeler gauges: 0.15 mm and 0.30 mm
• Spark-plug wrench and BMW plug-cap puller
• 10 mm wrench or socket for adjuster locknuts
• Torque wrench capable of 8 Nm
• Paper towels
• Compressed air
• Silicone grease for the plug boots
• A clean wooden chopstick or similar non-metallic probe

Do not use a screwdriver in the spark-plug hole. Colt’s chopstick method is sensible because it cannot scratch or damage the piston crown.

1. Prepare the Bike

Place the motorcycle securely on its centre stand.

Remove both plastic spark-plug covers. Before removing the plugs, blow compressed air into the plug recesses. Dirt, grit and small stones collect there over time, and none of it belongs inside the combustion chamber.

Wear eye protection.

Use the original BMW plug-cap puller from the under-seat toolkit. Do not pull hard on the ignition lead itself. The caps and, on twin-spark bikes, the stick coils can be damaged internally.

Remove both primary spark plugs. Remember to blow out any dust and dirt before removing the spark plugs.

2. Remove the Left Valve Cover

Start on the left cylinder.

Remove the valve cover. It may need a gentle tap with the heel of your hand or a rubber mallet to break the seal.

Have paper towels ready. A few tablespoons of oil will spill from the cover.

Clean the inside of the cover. Check that the central rubber tunnel gasket comes away with the cover or refit it to the cover before reassembly. The outer perimeter gasket can remain on the cylinder head if it is clean and undamaged.

Do not force the cover off or back on. These gaskets are reusable, but only while they remain supple and undamaged. BMW OE gaskets are preferable to cheap aftermarket versions.

3. Find Top Dead Centre on the Compression Stroke

This is the step that matters.

Put the gearbox in top gear and rotate the rear wheel forward in the normal direction of travel.

Watch the two intake valves on the cylinder you are working on:

1. They move down as the valves open.
2. They return up as the valves close.
3. The piston is now rising on its compression stroke.

Insert a wooden chopstick gently through the spark-plug hole so it rests on top of the piston.

Continue turning the rear wheel slowly. The piston will push the chopstick outward. When it reaches its highest point, that cylinder is at top dead centre.

If the chopstick starts moving down again, you have passed TDC. Turn the wheel back slightly and find the high point again.

The key requirement is not merely TDC. It is TDC on the compression stroke.

At correct TDC compression, both inlet and exhaust rocker arms on that cylinder should have slight free play. If the rockers are tight, you are on the exhaust/overlap stroke. Rotate the engine one full crankshaft turn and try again. BMW Oilhead owners consistently identify this as the most common valve-adjustment mistake.

Later R1100S engines may also have useful cam-sprocket alignment arrows. When the correct cylinder is at TDC compression, the arrows should point horizontally outward. That is a valid cross-check, but do not rely on it blindly if you are new to the procedure.

4. Check the Valve Clearance

Each cylinder has:

• Two intake valves
• Two exhaust valves

Check both intake valves together, then both exhaust valves together.

A pair of feeler gauges, one at each valve, is usually easier than using one blade and moving it back and forth. It lets you feel whether both valves are set evenly.

The correct feel is what Colt calls a snug slip-fit:

• Not loose enough for the gauge to fall through
• Not tight enough that you need to force it
• A smooth, slight drag is correct

Use:

• 0.15 mm on the intake valves
• 0.30 mm on the exhaust valves

5. Adjust if Necessary

Loosen the adjuster locknut slightly.

Turn the screw until the feeler gauges give an equal, snug slip-fit on both valves in the pair.

Hold the adjuster screw in position and tighten the locknut to 8 Nm.

Do not overtighten it. This is a small fastener. Colt’s warning is right: no “Magilla Gorilla” antics.

After tightening, recheck the clearance. Locking the nut can slightly alter the setting.

Repeat until both intake valves match each other, then do the same for both exhaust valves.

6. Refit the Valve Cover

Wipe the sealing surfaces clean.

Refit the cover straight and square. It should seat easily and almost click into place.

If it will not sit correctly with minimal pressure, stop. Remove it and check the central tunnel gasket. It is very easy for that gasket to sit crooked and prevent proper seating.

Do not force the cover.

7. Repeat on the Other Side

The other piston may also be at TDC, but it will initially be at the wrong TDC: exhaust/overlap.

Turn the rear wheel forward one full engine revolution until the opposite cylinder reaches TDC on its compression stroke.

Again, verify that both intake and exhaust rockers are loose before measuring anything.

Repeat the same procedure.

8. Refit Spark Plugs and Caps

Before reinstalling the plug caps, apply a very thin smear of silicone grease inside the cap where it grips the porcelain section of the spark plug.

This makes the caps easier to remove next time and reduces the chance of damaging them.

Refit the spark plugs and caps carefully. Before refitting the valve covers, reinstall the spark plugs carefully by hand to avoid cross-threading the aluminium cylinder head.

Tighten the spark plugs to:

20 Nm

Do not over-tighten them. The correct torque matters more than brute force, particularly on an older aluminium head.

Return the gearbox to neutral before starting the engine.

Do the Throttle-Body Synchronisation Afterwards

Valve adjustment should be followed by a throttle-body synchronisation.

Do not attempt the throttle-body sync on a cold bike or by idling it in the driveway for twenty minutes. Take the bike for a proper 10–20 mile / 15–30 km ride to bring the engine fully to normal operating temperature.

Then perform the synchronisation according to the method and tools you use.

Valve adjustment establishes the mechanical baseline. Throttle-body synchronisation fine-tunes the running once the engine is hot.

Common Mistakes

• Adjusting valves on the exhaust/overlap stroke
• Working on a warm engine
• Using one gauge and setting the two valves unevenly
• Forcing the feeler gauge
• Overtightening the 8 Nm locknuts
• Damaging plug caps by pulling on the wires
• Forgetting the central valve-cover tunnel gasket
• Syncing throttle bodies before adjusting the valves
• Forgetting to return the gearbox to neutral

Final Note

The R1100S valve train is robust and forgiving, but it likes accuracy.

Do not chase absolute perfection with excessive adjustment. A calm, even setting with a consistent snug slip-fit is better than repeatedly disturbing the adjusters trying to make every feeler gauge feel mathematically identical.

Colt’s original advice remains the right summary:

Care, accuracy and attention to detail are required.

That is all this job needs.