1994 R1100RS rattling sound in neutral

A few days ago I bought a 1994 R1100RS, 15K. The bike runs great, I am happy, but in neutral with engine running there is a sound like - a soft version of a playing card being held against bicycle spokes. When I pull in the clutch it goes away; let out the clutch, it comes back (neutral light is on). Also, I noticed that the it sometimes takes a little exploratory nudging of the gear shifter for the neutral light to come on. During exploratory movement of the gear shift lever, the sound remains unchanged. Is this something partial to oilhead transmissions? I had a '85 K100RT (40K) - never had this particular issue. Any help appreciated until my repair manual arrives.

Thanks, Dave

Current: 1994 R1100RS; 2009 KLR650
Past: 1971 Yam RD350; 1976 Yam XS650; 1981 Yam XJ750; 1991 Yam XT600;
1985 K100RT

I've had two oil heads, they all do that ! I'm not sure what it is but I hear it's from the dry clutch and the tranny. My R1150RT-04 with 63,000 miles has always done that, kinda like a Ducati, with its ring-a-ding sounding clutch. By the the way the R1100RS is a sweet bike!

That is a natural gear rattle as the engine speeds up and slows down each power pulse and compression stroke while the transmission shaft tries to coast along. On later models BMW installed rubber O rings to damp the noise - which works for a few years until the O rings harden.

The same noise was common when the 5 speed transmission was introduced in 1974 and Oak Okleshen wrote a thorough explanation way back then.

Don't worry about it. They (1994 R1100RS bikes) all do it.

My #1 son has a '94 R1100RS that has ~60K miles and it has the same noise. Good to hear that it is normal.

My 94 R11RS also makes the rattlilng noise in neutral when the bike is at operating temperature. It is a resonance (i.e., sounds amplified) when the vibrations are at a certain frequency. I can usually make the gearbox rattling go away by pulling in the clutch, blipping the throttle, then releasing the clutch.

Until the resonant frequency is restored the loud rattling has gone away. In my case this might be a minute or so. By the time the resonant frequency is restored, the stoplight has changed and I am on my way once again.

As PGlaves mentioned, BMW's "fix" to this issue was to add some o-rings. As I recall, the bikes that got the "fix" were somewhat more difficult to shift. I prefer my "fix" over the BMW fix.

Here is what Oak Okleshen wrote about this issue in 1974 regarding the new /6 transmissions:

"The noise is the result of an unloaded transmission and the backlash in the mating parts clattering slightly due to variances in engine speeds when at idle. The engine, though we think of it as running at a constant speed, varies in a miniscule amount when it is unloaded and at low speeds near idle. This happens between the power pulsations from the pistons. The flywheel helps to prevent the uneveness but does not cure the problem entirely for it would take a much larger and heavier flywheel than necessary to make the machine run properly and would detract from acceleration performance. As a result, the engine pulsates and the transmission attempts to run at a constant speed. Between pulsations the backlash in the transmission causes the components to clank lightly and cause noise.

The noise can become more noticeable if ...unbalanced left to right. This causes engine pulsations to become more uneven and, hence, there is more noise in the transmission in neutral, clutch engaged."

Thanks

Thanks to all for the peace of mind. I already love this bike. The explanations make perfect sense.

Cheers,
Dave