The important point is that this is not a cam-chain replacement. You replace the hydraulic tensioner assembly that keeps the left-side cam chain properly tensioned.
On early Oilhead engines, including many R1100S models, the original left-hand tensioner can drain down after the bike has been parked. On the next start, the chain may rattle briefly until oil pressure refills the tensioner. BMW later introduced an improved design with a better piston arrangement and sealing behaviour. It is one of the most common preventative upgrades on an older R1100S.
The right-hand tensioner is not normally upgraded. The left side is the issue because of its orientation and tendency to lose its oil charge while parked.
What the Upgrade Does
The improved tensioner reduces the familiar left-cylinder cam-chain clatter on start-up and at idle.
It does not turn the R1100S into a silent engine, nor does every bike need it urgently. But where the original tensioner is fitted, it is a worthwhile reliability and refinement upgrade.
A brief rattle at start-up is the usual reason owners fit it. If the noise is persistent, loud or accompanied by poor running, investigate further rather than assuming the tensioner alone is responsible.
Parts Required
The usual BMW upgrade set consists of:
- Cylinder, left cam-chain tensioner:
11 31 7 688 629 - Piston, left cam-chain tensioner:
11 31 7 656 922 - Copper sealing washer:
07 11 9 963 308
These are commonly sold together as the left-side Oilhead cam-chain-tensioner upgrade kit. Confirm against your VIN before ordering.
Before You Start
Work on a cold engine.
You need clear access to the left throttle body, because it sits directly in front of the tensioner. Have a new throttle-body O-ring available before starting. The existing O-ring can expand once disturbed, making reinstallation awkward or preventing a proper seal.
You will also want:
- A 17 mm spanner for the original tensioner
- A 15 mm spanner for the upgraded tensioner
- A magnet or magnetic pick-up tool
- Clean rags
- A small amount of engine oil
- A torque wrench, where access allows
The original and updated tensioners use different hex sizes: the old unit is typically 17 mm, while the upgraded cylinder uses 15 mm.
Video: Cam-Chain Tensioner Replacement
This video shows the general BMW Oilhead cam-chain-tensioner replacement process and is useful to watch before starting. The R1100S access is tighter because the left throttle body sits directly in front of the tensioner, but the upgraded tensioner design and installation principle are the same.
Step 1: Remove the Left-Side Body Panel
Remove the left-side bodywork or “bodyguard” panel to give yourself access to the throttle-body and airbox area.
Keep the fasteners organised. This is a small job, but losing a fairing screw is still irritating.
Step 2: Disconnect the Throttle Body From the Air Intake
Remove the two screws securing the connection between the left throttle body and the air-intake tube.
Once loose, slide the intake connection back into the airbox. This creates enough room to withdraw the throttle body from the cylinder head.
This is the practical trick that makes the job possible without dismantling half the motorcycle. R1100S owners consistently describe moving the left throttle body aside as the key access step.
Step 3: Remove the Left Throttle Body
Carefully pull the throttle body free and move it aside.
Do not strain the throttle cables, injector wiring or fuel connection. Support it so it is not hanging by anything.
Check the throttle-body O-ring. If it has swollen, hardened or lost its shape, replace it before reassembly. A poor seal here can create an intake leak and poor running.
Step 4: Remove the Original Tensioner
With the throttle body out of the way, the left cam-chain tensioner is accessible.
Loosen and remove the old tensioner cylinder.
Part of the original assembly will remain in the bore after the outer cylinder has been removed. This is normal. Use a magnet to lift the remaining piston from the hole.
Do not poke blindly into the bore with a screwdriver or sharp pick. You do not want to damage the sealing surface or leave debris inside the engine.
The original guide notes that a modified tool can make this easier, but a simple magnetic pick-up tool is usually sufficient.
Step 5: Install the New Tensioner Components
Install the new piston into the bore first.
Then fit the new tensioner cylinder with its new copper sealing washer. Make sure the piston sits correctly and the cylinder threads in smoothly by hand.
Do not force it. If it does not start cleanly, stop and realign it.
Tighten the tensioner to the BMW specification for your exact model and manual. Do not guess the torque from a forum post; the tensioner threads into aluminium and the sealing washer needs the correct clamping load.
BMW’s workshop documentation treats the cam-chain tensioner as part of the timing-chain assembly, so use the factory repair manual as the final authority for torque and any model-specific variation.
Step 6: Refit the Throttle Body
Refit the throttle body with the O-ring correctly seated.
Slide the intake connection back into position and reinstall the two screws.
Check that:
- the throttle body is fully seated;
- the O-ring has not rolled or pinched;
- the intake boot is properly positioned;
- throttle cables are routed normally;
- nothing is trapped behind the throttle body.
Then refit the left-side panel.
First Start
The new tensioner may need a moment to fill with oil on the first start.
A brief click or light mechanical noise immediately after installation is not unusual. Let the engine idle for a short period and listen.
The expected result is less left-side rattle on future cold starts and a quieter mechanical sound at idle.
Common Mistakes
Replacing only the outer cylinder
The upgrade is a matched cylinder-and-piston assembly. Fit both new components.
Dropping the old piston into the engine
Use a magnet and work slowly.
Reusing a swollen throttle-body O-ring
It is cheap compared with chasing an intake leak afterwards.
Using the wrong side
This guide is for the left-hand cam-chain tensioner. The right side is normally left alone unless it has a separate fault.
Treating it as a cure for every engine noise
It reduces cam-chain slap. It does not fix valve-clearance issues, throttle-body wear, low oil level or other mechanical problems.
Bottom Line
The left cam-chain tensioner upgrade is a small, proven improvement for an ageing R1100S.
It is not a dramatic performance modification. It simply removes one of the better-known Oilhead annoyances: the brief left-side cam-chain rattle caused by the original tensioner losing its oil charge after standing.
Do the job carefully, keep the throttle-body seal in mind, use the complete updated assembly and follow BMW torque data for final tightening.