Gearbox Problems

[Chris Hazard]

Currently got my 2003 Twin Spark GS in my dealers workshop having its gearbox stripped to replace a rumbing bearing and thought that I just might be unlucky.

On seeing another GS in the workshop apparently having minus its gearbox in pieces I'm now starting to worry that these things aren't as robust as the marketing hype would have me believe.

I've had the bike from new and it gets ridden in all weathers except ice & snow, done over 13000 happy miles on it , but am now concerned that a gearbox strip every year will be the norm.

Am I being unneccessarily worried and have maybe just been unfortunate, or is this the start of expensive things to come?

Good job its still under warranty.

 

[Mick Fagan]

Do you, or have you, ever changed gears without using the clutch?

This shouldn't make any difference to the bearings in the short term, but, if you have bent a selector fork by clutchless changes then it's possible that one of the gears is not fully engaged and putting slight side pressure on one of the shafts.

This in turn puts pressure on the bearings. This is the kind of thing that destroys racing G/boxes as they are pushed to the extreme limit of their tolerance,in a short time period.

I haven't heard of any 2003 or 2004 twin spark GS's doing any bearings in the short or long term. The longest one I know of is from an aquaintenance who has a 2003 1150 Adv with 145,000 Klm's on the clock. I know of two others that have around 80,00 to 95,000 after just over 1 year old and their gear boxes are perfect. All of them however are BMW riders from many years of experience and they change gears the dry single plate clutch way.

Mick.

 

[trotsky]

...they change gears the dry single plate clutch way.

Perhaps you could expand on that Mr Fagan, or anyone else.

I came from a Honda to the BMW and, apart from knowing that I need to use the back brake rather than slip the clutch for slow speed control, my gear and clutch work is just a bit more positive than it was on the 'Onda.

Is there a recognised "good way to change gear on a BMW" which I should be following?

 

[Chris Hazard]

Thanks for your reply Mick . Its interesting to know that higher mileages and gearbox problems do not necessarily go together.

I don't use a clutchless gearchanging technique as whilst being no technician, I'm sure that ultimately not using the clutch won't help in the long term.

 

[Mick Fagan]

If you are running a dry single plate clutch as opposed to a multi plate wet clutch you should notice that there is far less slippage available on the dry clutch compared to the wet clutch.

Virtually all modern bikes run a multi plate wet clutch. The clutch as it's let out, has multiple points of friction that will start to grab in a more controlled manner, especially when in a constant use situation like heavy traffic.

Have you not noticed that the clutch on a BMW bike gets quite grabby and slightly difficult to control in heavy slow traffic?

The other problem that a BMW bike has, is that the input shaft in the gearbox, runs at engine speed, compared to most other bikes where the input shaft runs at ½ engine speed. High revs in a low gear then a quick change up a gear and one can sometimes hear the problems encountered by differing shaft speeds in the box.

In higher gears when the road speed is much greater and therefore the output shaft is travelling much faster, the input shaft speed relative to the output shaft speed, is far closer therefore gear changes become much easier and also very much quieter.

Although in my time I have done some real damage to BMW gear boxes I have to say that on the whole a BMW gear box is relatively well built. Through personal experience I expect a BMW gearbox to last around 250,000 Klm's before a bearing replacement is is required. Nearly all of my gear boxes over the years have lasted until about this time.

The insides of the 1100 series bikes are virtually identical to the previous bikes, in general that is, therefore I expect them to be pretty much the same or slightly better as manufacturing tolerances are now better or finer than decades ago.

Mick.