BMW K bikes (Bricks)

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1Back to top Go down   Bleed  Brakes Empty Bleed Brakes Mon Nov 24, 2008 9:04 am

yankeeone

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Hi , I have a 87 k75 c with drum rear and I changed the fluid in the front .I had a few questions. First , how much free play should there be in the leaver ? also I used a small vacuum pump to pull the fluid through the caliper, and I got a lot of air by the treads on the bleeder, is there a way to seal them ? I think they are the stock type, the rubber cap is held on under them . Any thoughts?
Thanks

    

2Back to top Go down   Bleed  Brakes Empty Re: Bleed Brakes Fri Apr 10, 2009 5:10 am

wikur

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Hi Yankeeone!
Try opening the bleeder just maybe a quarter of a turn or just as much as when air bubbles and break fluid is seen in the bleeder hose.I haven`t used a pump myself,only the standard method of pumping the lever and open and close the bleeder.Good luck!
Cheers,wikur!

    

3Back to top Go down   Bleed  Brakes Empty Re: Bleed Brakes Fri Apr 10, 2009 7:57 am

Crazy Frog

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Yesterday I replaced the break lines on my K100.
I installed the stainless steel braided one.
I was amazed that in the front all the air was coming up on the master cylinder on its own.
Air had the tendency to rise.
I found that taking a 5 minutes break during the procedure permit to the multiple little bubbles of air to rise to the highest point. It's then easier to bleed.
Press on you brake lever, then slightly open one bleeder. Close it tight before releasing the brake lever or you will suck the air back into the caliper.

Bert

    

4Back to top Go down   Bleed  Brakes Empty Re: Bleed Brakes Fri Apr 10, 2009 7:44 pm

K-BIKE

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For those of us with ABS the bleeding is a little more complex as the pipe run is somewhat tortuous but the comment by Bert is so true. Air rises and it is worth letting the air bubbles rise and even rapping the brake lines and callipers with a small screwdriver handle to encourage any bubbles stuck to the top is a good idea. I do know that the 1985 Volvo's have a quite complex braking system (we have one of these and the factory brake bleeder attaches to the master cylinder and sucks fluid from the calliper up to the master cylinder.

The problem that yankeeone commented on the air sucking back past the threads of the bleed nipple can be fixed by spreading a good bead of silicone grease around the junction of the bleed nipple and the calliper DO NOT get the grease on the disk and wipe off the excess when finished. The grease will stop the air getting down the threads.

Combine that with Bert's advice about closing the bleeder first is good practice. The risk with the suck out method is the M/C on a motorbike is tiny and it is easy with enthusiastic bleeding to drain the M/C and pull air down the line. Hence I tend to favour Bert's method of pumping the lever.

Last points, after bleeding and doing the the tap and bleed wait for the bubbles to rise and bleed again. I favour putting the whole system under pressure with the lever and letting it off quickly wait a few minutes and bleed again, this can break free any last bubbles that are stuck as they squish right down under pressure and swell up suddenly and hopefully break free. Some even favour leaving the system under pressure overnight before re-bleeding. I have not needed to do that as yet. I will comment I found bleeding the rear brake of my ABS equipped K 100 a pain when I replaced the M/C seals, it took a long time to get the air out even after bench bleeding.
Regards,
K-BIKE

    

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