Stop The Rattle

1100/1150 Cam chain tensioner upgrade

Created 26/04/06 - Amended text 28/08/06

If you own a 1100 or 1150 BMW you have probably noticed a rattle on starting up the bike. This mostly quietens down after a few seconds but it's quite annoying, and considering it's a BMW it's embarrassing too!

Why it rattles.

The rattle comes from the left side cam-chain flailing about when the bike is idling. It seems when the engine is stopped the oil in the left side tensioner drains out via the slot milled in the piston. When the engine is restarted the cam chain pushes the tensioner piston up its bore allowing the chain to rattle. Once the engine has been running a few seconds the tensioner re fills with oil and the rattling stops. This problem doesn't affect the right hand tensioner, because it's the other way up and the oil cannot drain out.

The original tensioner components, Note the oil feed hole in the body and the drainage slot milled in to the piston on the left.

This picture shows a rear view of the 1100 engine with the original tensioner assembly and its location in the engine. Note the right hand tensioner is under the chain, pushing upward and doesn't drain.

General layout of the cam chains and tensioners as viewed from the front left side. We will be replacing the parts top right 10, 14, 12 and 15.

Stopping the rattle.

Providing nothing else is wrong, we can fit an upgraded tensioner assembly as shown in the picture below. The new piston is spring loaded internally, oil enters the tensioner body by the small hole as it does in the original, but now there is no drainage slot for the oil to drain back out of, thereby maintain tension on the cam chain.

Piston p/n 11 31 7 656 922 - Cylinder p/n 11 31 7 688 629.

Part number for a new gasket (not shown) is 07 11 9 963 308.

Fitting.

Once you have removed the left side body work and injector body, this is what you see. Unfortunately the left side tensioner (arrowed) is right under the pivot for the front suspension wishbone, and just a little tricky to get at. A 17mm ring spanner was used to remove the old tensioner body. The head was a little corroded and flaky, so once it was loosened off we blew it clear with compressed air to stop any rust or dirt dropping in to the engine. You could use a bicycle pump to achieve the same effect.

When the old tensioner is fully unscrewed it can be lifted up and rested on the edge of the hole, but It won't come out until we have removed the spring from under it. So now the tricky bit!

I used a paper clip bent into the shape of a small hook to pull the spring down from the inside of the tensioner body, then insert a screwdriver between the top of the spring and the tensioner body to keep them apart. This is tricky to do, but the body came away easily after that.

With the body out it's easy to remove the old spring.

Fishing  the old piston out with the aid of a magnetic probe.

Fitting the new piston and body without a spring is easy: oil the new piston and tensioner, and drop the piston into the hole (open end upward) then drop the body on top of it. Press down with your finger and turn with a 15mm ring spanner until the threads picks up, finally tighten the tensioner body to 32Nm or 23.6 ft-lb. Quite how you're going to get the head of a torque wrench and socket in to that space is a mystery to me. I'm sorry, but we just guessed it. I hardly think it's critical.

Lastly I would recommend balancing the injector bodies soon after completing this job, the cable has been disturbed and likely needs minor adjustment.

After fitting.

When you first start the engine after fitting the new tensioner parts it will rattle briefly as it used to do, but once the new tensioner has filled with oil it goes quiet, and it stays that way. Next time you start up it will be quiet from the first firing.
What bliss it is to hear the valve gear rustling quietly away!

Cost of parts.

Obtained from Motorworks UK: cost (inc vat) was:

Piston    £25.53

Cylinder £17.17

Gasket   £0.17

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Notes.

1. I strongly recommend you read the two Cam Chain Tensioner PDFs in Adventure Riders Hall of Wisdom, the photo journal in the first one is very good indeed.

2. To help clarify what can be quite muddy water, BMW produced an earlier modified tensioner kit to quieten the rattle (see the picture below). This was a set of three components grouped under p/n 11 31 2 325 563 and fits the 850/1100/1150 and 1200c Cruiser etc.

This set has now been superseded by the two modified tensioner parts described above.

3. According to the 2006 BMW ETK parts DVD the modified tensioner parts will fit the following models:

4. You can't swap old and new parts, the piston from the new tensioner will not fit the old body, the piston diameter is different and the new body is a different length.

5. Lastly, thanks to the contributors of the Adventure Riders Forum for the content of this webpage, without their input this page wouldn't exist and my engine would still be rattling! Thanks Guys!

6. At Powerbox.de a German write up of this procedure with thanks to Gerd Sperber
 

Disclaimer

Any modifications you carry out on your machine are done so entirely at your own risk

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