4K RPM Rattle

[R65North]

Hi Guys,
My bike has a noise right around 4000 rpm. It sounds like a rattle, almost like a loose baffle; like sheet metal vibrating. Can't find a source though. Seems to be from the frost but hard to tell. It happens in 3rd and 4 for sure, not sure of the other gears but always at the same revs. It only happens when the clutch is engaged i.e. the bike is putting power down. I was thinking timing chain/tensioner etc but it is at such a localised area of revs I am now les sure.

Bike is an early model - '79 with 66K miles

Is this normal or something to dig in to further?
Cheers
Dave

[nhmaf]

So it will not make the sound when running, in neutral, on the centerstand, at any RPM ?

It still could be a loose muffler part or any of a number of possible things that just happens to have a narrow frequency of vibration, the engine itself usually has a vibratory "peak" around 4500 RPM, give or take  a hundred RPM or so.

Timing chain/tensioner could be the source of the sound but it is often an "always there, sometimes louder than others depending on RPM" situation.

Might be time to get out the mechanics stethoscope / large screwdriver to listen at the engine case near the timing cover and other areas (with the bike not moving, of course!!)

[Bob_Roller]

I'd check the exhaust system, I have a loose baffle in my left muffler on the '81 R65, it only rattles at a certain rpm range .
Check the exhaust system for security .
Check center stand for looseness .
headlight shell for security .
Check the fuel cap .
If you don't find the culprit, I'd spend some time tightening the fasteners on the bike .

[R65North]

Thanks Guys good to rule out any known problem, think we were all thinking along the same lines that its harmonic vibration. Odd it does not do it when the bike is in neutral on the centre stand. I cannot rev it above around 4K as running in the gears. Of course how you should do that is another subject entirely and one I've had my fill of! Cheers, Dave

[Bob_Roller]

The R65 is known for a noticeable vibration in the 4200-4500 rpm range .
Some bikes exhibit this more than others .
My '81 R65 had this issue, but at 88,000 miles, I can't feel it anymore .