1150 GSA 4th gear rumble / Vibration

[Trippy]

..is 4th gear direct 1:1 and fifth an overdrive on these old nails ?

Well you might only have 5 gears on your old bike but I seem to have 6 on my new Adventure which I believe has a slighly different gear ratio to an 1150 on both 1st and 6th.


Oh and I did get rid of the Toyota .... just to buy another

 

[Pukmeister]

All machines with gears and bearings have some form of resonant frequency, plus harmonics as multiples of those frequencies. These frequencies may be more or less noticeable depending on how well the vibrations are isolated from the end-user or operator of the machine. The vibration you speak of happens at a certain point in all gears, its just that the amplitude (size) of the vibes have enough energy to be physically felt in your 4th gear/ 35-45 mph range and at a frequency your ears can easily detect.

I used to carry out vibration analysis on ships engines (gas turbines) and gearing and you'd be amazed at how one of Rolls-Royces finest engineering craftsmanship can rumble like a bag of bolts at certain revs. Next time you are sat on a plane and the engines start up, listen out for the rumble as the compressor/turbine spools accelerate through their first resonant frequency.

If your bike shifts cleanly through the gears and only rumbles at a certain small RPM band, I wouldn't lose any sleep over it.

 

[Trippy]

.

I wouldn't lose any sleep over it.

I'm not.

 

[Steptoe]

, I wouldn't lose any sleep over it.

I would. I'd be on medication, cancel all the trips planned on the bike, and fretful.

Try searching the internet, that'll help. And you'll find out the full extent of your problems with a SE ADV, and the needless worry about the rumble will be chickenfeed compared to eveything else.

 

[Slime Bomb]

I have the same, done it ever since i bought the bike with 6000mls on it and still does it now with 34000mls. It's nice to know your not the only one

 

[(RIP) Kaister]

Well you might only have 5 gears on your old bike but I seem to have 6 on my new Adventure which I believe has a slighly different gear ratio to an 1150 on both 1st and 6th.

no rumbling bearings or anything to worry about yet on my pile of ancient old rubbish

 

[rokraider]

Being shaft drive with a couple of universal joints (rather than constant velocity joints) in the drivetrain, I suppose the angle of the shaft in relation to the output shaft and the pivot at the wheel end could be affected by suspension height. Does the vibration change with weight/ride height? I have noticed my GSA which is running on Ohlins vibrates differently when low on fuel and I haven't bothered to back off the rear shock when riding solo with the bins empty (ie riding at its highest).

 

[Bryn]

2003 1150 ADV with 15000 miles... same thing in 4th gear.. sounds like not much to be worrying about...made me feel better anyway

Bryn

 

[cookie]

my 2007 1200 does it too.

 

[Invicta Moto]

Trippy,
my 99 1150GS has been doing the same for years. Got 65,000 miles on the clock now and it's no worse, no better. It's more pronounced going up hill at a constant speed (around the speeds you mention).
Kev

Mine does the same, only in 4th. It does it on the flat as well at about 35-40mph. I notice it most nerar home when the engine isn't fully warmed up and I am in the 40 limit area...

I mentioned it to several UK BMW Dealers, plus one in France and they said it was nothing.

Mine too is a 99 model 1150.