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1981 R100RS Engine Rattle
This rattle only happens between 2800 and 2900 RPM. Bike has 300,000 plus Km. on it. Could it be the timing chain? Dick V.

You might get a better response if you post this message in the 'Post 1970 Airheads' section.

thanks, how do I get to 'Post 1970 Airheads' section please? Dick V.

Click on "BMW MOTOTCYCLES" at the top of this page, right below the Boxerworks logo. It's the first forum on the list.

I don't know where Dick Vandevelde is, but I'm in the post 1970 section right now

The post was moved.

dickvandevelde wrote:1981 R100RS Engine Rattle
This rattle only happens between 2800 and 2900 RPM. Bike has 300,000 plus Km. on it. Could it be the timing chain? Dick V.

Are you sure it's the engine? The fairing can amplify noises from anywhere down there. eg loose fuel cap, loose front engine cover...A loose timing chain would be likely to rattle at lower rpm I'd've thought.

Has the engine ever been opened?

When was the last oil change and what W oil was used?

I don't know the history on this engine, I do change oil every 5000 miles. 20/40 oil. The transmission was rebearinged twice. I've checked all those things that might be loose, all are tight. It sounds like its in the left front of the motor.
The book shows a chain tensioner and a plunger and a spring behind it. Is it oil pressure fed?

dickvandevelde wrote:
The book shows a chain tensioner and a plunger and a spring behind it. Is it oil pressure fed?

The cam chain tensioner piston is oil damped, but there is no pressure oil feed. It is also spring loaded.
A worn chain could be the source of your noise, or not.
Under what circumstances does the rattle occur? Idling? Under load when riding?

Just between this RPM range, 2800 and 2900 RPM under load or not. The noise is in the left front of the motor.