ABS vs non-ABS front master cylinder

[RiceBurner]

Anyone know the difference?

Currently utterly failing to bleed up a Non-ABS Rockster, and I fear I may have an ABS m/c (2nd hand) on the bike.

anyone have any knowledge on this perhaps?

[el-nicko]

Does this help?

http://www.realoem.com/bmw/showparts.do ... g=32&fg=72

[DaveH]

I have removed the ABS system from my GS after servo problems.
The master cylinder provides plenty of pressure to operate the brakes normally.

Only the brake light activation switch needed to be converted and I did this at no cost anyway

see link here

http://dhmoto.net/doc/Abs_Removal.pdf

If you do have the ABS master cylinder iit should make no difference to the bleeding procedure anyway.

Make sure the bend in the front brake line does not rise above the banjo union at any point or you may get an air bubble that is hard to shift.
Try removing the MC from the bars ahd holding it up above the headstock so the line is straight to avoid this.
Better if you can get someone to assist with this.

Either reverse bleed or use vacuum extraction if you have the right equipment.

A cheap 50ml syringe can be adapted to reverse bleed the system if you do not.

[nab 301]

Afaik as I know the only difference is the stop light switch , ( from forum threads over the years and the parts websites , plus the parts fiches list the repair kit as the same for abs/non abs at 16mm dia.
Plenty of conversions done without changing the BMC , so if you have an abs cyl, it should work...
I had problems after a dry rebuild on my vfr , loosening the BMC banjo bolt didn't help , in desperation I turned to the internet and found a thread which recommended tapping the brake lever rapidly just to open the master cylinder slightly , a steady stream of airbubbles will appear in the reservoir and then you'll have a brake . Just tie the lever back for a few hours , tap the calipers and pipes with a rubber mallet to keep the bubbles rising and that should be it.... imo
I've used that method a number of times since on different bikes with great success.

[el-nicko]

I remember reading somewhere that; "When bleeding, the lever (foot/hand) should'nt be 'pumped' to the full extent of it's stroke but in short strokes on account of brake fluid being a 'moisture magnet' corrosion can, over time, form in that part of the cylinder the piston does not normaly reach and this can damage the seal lip." I too removed the I-ABS from my bike without any problem other than an initialy spongy front brake but cable-tieing the lever back overnight cured that and now I can stand the bike on the front wheel. Not always a good thing. 'cos extraX2 care is needed in the wet.

[Dai wiskers]

I nearly always fill the master cylinder and leave the nipple slightly loose for a hour or so cup of tea and a sandwich later blead as normal usually this will work with the odd stuban[spelin agin] one and you can get a good feel at the lever

All tips in previous posts are good as well Dai

[RiceBurner]

Cheers for all the suggestions.

Over the past years, while I've had the suspect m/c on the bike I've tried every single one of them, and more!

I'm really beginning to think that the two M/c are different somehow, I can see a logical reason for the ABS m/c to have a certain amount of "play" in the piston movement - and I am absolutely certain that there is far too much movement visible through the holes in the m/c before the seal on the piston starts actually compressing the fluid. I've even tried adjusting the screw fitted to the brake lever so that the piston is "pre-positioned" further in, but it had some really weird effects and didn't work.

I've lost the will to struggle quite frankly and have just shelled out for a OE BMW part direct from the factory. If it STILL doesn't work then I'm not sure what'll be heading for the top of a skyscraper - me or the bike.

[el-nicko]

Did you fit a new seal kit?

[RiceBurner]

Did you fit a new seal kit?

Have tried new seal kits in both the callipers and the m/c. they never made a huge difference.

[r550s]

(Apologies if you've already considered this)

Have you checked the tiny hole (the important one) for fluid movement to/from the reservoir as you pump the lever?

The tiny hole can get blocked - you're using a s/hand master cylinder that might have been stood for a while?

If you've altered the pushrod, make sure that the piston still retracts far enough to uncover the tiny hole. I push a small wire through to feel for the seal.

Be prepared to slacken or completely remove the master cylinder from the bars - getting an upward angle for the hoses and banjo can help loads.

Small pumps - just trembling the brake lever can help to get the bubbles coming out into the reservoir.

If you've got fluid in the calipers, pressing the pistons back in can do the same as reverse bleeding and get things going.

It can still be a bugger though!

[RiceBurner]

well, brand new BMW m/c hasn't helped a bit.

i can watch the piston move past the two holes absolutely fine, I can watch the little spurt of pressure from the tiny hole. Then - nothing. very , VERY little pressure, enough to move the pistons in the callipers but nowhere near enough to stop the wheel turning even at only 2mph.

I've tried everything I can think of and have read on the 'net - tapping the lines, turning the callipers about, pumping the pistons out to back pressure the system etc etc etc. nada.

The Goodridge lines are two individual lines leading from a double banjo at the m/c to each calliper. Can Goodridge braided lines fade with age like rubber lines?

Does anyone have any further ideas of where there might be trapped air?

[el-nicko]

Well, if you let us know where you're located instead of being coy about it you might find a fellow Trixter would pop round and give you a little help, or at least some moral support. I mean for all I know you could be just round the corner from me

[nab 301]

The Goodridge lines are two individual lines leading from a double banjo at the m/c to each calliper. Can Goodridge braided lines fade with age like rubber lines?

Does anyone have any further ideas of where there might be trapped air?

With a simple two line system like that and the caliper pistons pushed back where can the air be? You seem to have covered everything , unless the seal between the caliper halves has somehow been misplaced and is blocking the drilling.
You're definitely using brakefluid in the system?....

All braided hoses afaik have a rigid "nylon" liner which doesn't deteriorate like oe rubber type hoses.

[RiceBurner]

Well, if you let us know where you're located instead of being coy about it you might find a fellow Trixter would pop round and give you a little help, or at least some moral support. I mean for all I know you could be just round the corner from me

I'm in Guildford.

[el-nicko]

Well, if you let us know where you're located instead of being coy about it you might find a fellow Trixter would pop round and give you a little help, or at least some moral support. I mean for all I know you could be just round the corner from me

I'm in Guildford.

Anybody live near Guildford and can give RiceBurner a hand then?