BMW K bikes (Bricks)

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1Back to top Go down    Brakes again on Wed Feb 03, 2016 10:31 pm

Packo

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Replacing standard front brakes with 4pot Brembos
After bleeding I can get a hard lever but if I keep the pressure on after say 20 minutes the lever will ease further back to the throttle grip. I have searched the old posts and have tried turning to left lock, tying the lever back overnight, hanging the calipers upside down with pistons pushed out as far as possible. I have been bleeding them only in the normal manner ie. from the bleed nipple at the caliper. I believe they can be bled in the other direction but not sure how to do it.
Open to suggestions
Don't know if this may be effecting things but the calipers are not seated perfectly central over the rotors- they are about 1mm off centre. The result being that the inside pair of pistons are pushing the pad a different distance to the outside ones. I can doctor them up to sit centrally to the rotor with a bit of work but if it is not going to make a difference I won't bother.
Please let me know what you think


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83 K100 HRD outfit
77 R100RS
2008 K1200S
    

2Back to top Go down    Re: Brakes again on Wed Feb 03, 2016 11:02 pm

RicK G

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A hard lever means there is no air in the system so that should be OK. having the lever slowly collapse would point to a leaking seal or a bad line that is slowly expanding with the pressure. Check for fluid under the rubber bellows over the master cylinder, if there is fluid there then the seal is bad because either the bore of the cylinder is corroded or scored or the seal itself is leaking. Check for fluid around the pistons at the caliper.
Hold the lever till it has collapsed to the grip and hold it there then check for distortions in the lines paying particular attention to areas around the fittings, the lines can have a leak in the inner which causes the bubble in the outer sheath but not to the outside.


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If everything seems under control then you aint goin fast enough:- Mario Andretti
Bikes 1986 K100RT, 1993 K1100 LT, 1994 K1100 LT, 1993 K75 RT, 1996 K75RT, 1986 K75 GS, 1979 Z1300 Kawasaki X 2 & 1976 SR 500 Yamaha for now
    

3Back to top Go down    Re: Brakes again on Wed Feb 03, 2016 11:07 pm

Packo

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Thanks Rick will give it a go


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83 K100 HRD outfit
77 R100RS
2008 K1200S
    

4Back to top Go down    Re: Brakes again on Thu Feb 04, 2016 12:55 am

Packo

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All lines etc ok. May have fixed the issue by forcing the pistons back into the calipers and then pumping them back up, did this a few times each looking for leaks etc. Must have forced some trapped air back the other way I think. Lever feels hard and appears to be holding firm and not collapsing. Promising at the moment anyway.


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83 K100 HRD outfit
77 R100RS
2008 K1200S
    

5Back to top Go down    Re: Brakes again on Thu Feb 04, 2016 6:35 am

charlie99

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good to hear ...hope it works out mate


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'86 K100 RT..#0090401 ..."Gerty" ( Gertrude Von Clickandshift ) --------O%O
    

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