front brake sticking

[wideparting]

hi people out yesterday on my bike[1200gs] and the front brake came on by itself and slowed me down,managed to brake hard using the front and it eventually went off again after a few stabs,has anyone else had this,and does anyone know what is the problem.this is twice this has happened.i use the bike year round. any suggestions gratefully received. thanks. j

 

[Pukmeister]

It could be several things.

Firstly and most easily, has the handguard on the right hand handlebar has rotated slightly and now rubbing on the front brake lever? A very common problem.

Next check, is the front brake microswitch (assuming it is servo abs) loose or misadjusted? They are held in place with a tiny allen screw from underneath, and can move if not set properly and operated the ABS servo pump (though this usually makes a noise/ flattens the battery rather than applies the brakes).

Final check. When was the last time the front brake calipers were undone and the brake pistons cleaned ? I suspect this will be your problem, you most likely have a sticking piston/pistons due to a build up of road salt/crap around the piston skirts/seals. They are sticking intermittently and causing the problem you describe. You most probably need to clean your brakes or get a dealer to do it for you if you don't know how.

If it isn't any of the above, take the bike to your BMW dealer and get it checked as the fault will not be 'user fixable'.

 

[wideparting]

thanks pukmeister going to have a look now and try what you have suggested,excuse my ignorance but where is the brake microswitch situated [im no mechanic as you can tell] thanks again j

 

[Pukmeister]

Assuming your bike is like mine and has Servo ABS, the brake microswitch is a tiny switch on the right hand handlebar behind the brake lever. Basically as soon as you start to pull on the brake lever, it causes the ABS pump to run and brings on the rear stop lamp. I doubt it will be a problem on your bike, but it is a small possibility.

Put the key in, let the ignition do the self test without the engine running, then gently pull the front brake lever. You should hear an electric 'wheeee' sound from under the fuel tank and the brake light should come on. Most importantly, when you release the brake lever the brake light must go out and the 'wheeee' sound should stop. If it doesn't your brake microswitch is either sticking or needs adjusting by the dealers.

Note that here should be a gap inside the handguard between the brake lever end and the handguard itself. If not, tap the handguard as necessary to rotate it up/down on the handlebar and reset the gap.

 

[wideparting]

i pukmeister thanks for your help.handguard seems ok and servo goes off ok so it may be as you suggested,crud on caliper pistons.it is due its 12k service shortly so i will mention this to the mechanic. thanks again. j

 

[Sgt Bilco]

It`s a common problem with brakes this time of year. They get full of crud.

Mine were cleaned up at the last service FOC so be nice to your dealer