1978 R100RS Engine Noise

[Ade B]

Hi All

As mentioned in earlier posts, here's a video of the noise I'm getting. Mileage is 75k miles.

[media]https://youtu.be/UK-52KEtzsY?feature=shared[/media]

Possible pinging, timing chain, something else?

The engine badge fell off just before filming!

Be interested in thoughts.

Cheers

Ade

[gspd]

Definitely NOT pinging.

First step is to pinpoint the source of the noise.
Remove the front engine cover and have a listen with a stethoscope to the beancan, alternator and timing chain casing area, PCV flapper valve area, valve covers, etc. to see if you can pinpoint the noise. No stethoscope? A log screw driver with the tip pressed against the suspect area and the handle in your ear will work for now.

[Ade B]

Thanks, good to know.

Have an engine stethoscope somewhere, will have a poke about.

[barryh]

Even an engine that does does have pinging would never exhibit it when the bike is stationary on the stand. The engine has to be under substantial load. With no load the engine will rev right up with just a fraction of throttle and that won't produce sufficient compression in the cylinders to promote pinging.

If you still think you hear pinging when riding the bike, just roll of the throttle a little. If the noise doesn't go away it wasn't pinging.

[Ade B]

Thanks, first noticed the noise 2up with luggage after fettling carbs, valve clearances and timing. As mentioned it is very specific to a narrow rev band coming in at around 2700 rpm and stopping a couple of 100 rpm higher. I hadn't noticed it before on the stand until this weekend. Its more audible from the LHS but that might be due to the garage wall being closer on that side and reflecting the noise back as on the bike it sounds like it comes from the RHS

If it isn't pinging, its a resonance of some sort, I'll update once I've had a prod with the stethoscope.

[SteveD]

The (edit: I read you now have a S fairing. RS fairing) can amplify any noise and make it difficult to isolate. Don't discount anything! eg, this fixed a weird noise mine had years back. Put a cable tie around the intake snorkels to take up any slack and see if it goes away.
It does sound metallic though, but you might get lucky.

Ensure the two bolts that hold the front cover are tight.

I suppose holding the rpm for a very short period whilst holding different parts to see if it disappears, eg press the front cover to see if it changes the noise?