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TECHNICAL MOTOBRICK WRENCHING In Remembrance of Inge K. => The Motobrick Workshop => Topic started by: RobP on April 18, 2016, 09:59:33 PM

Title: No Joy After New Front Brake Lines
Post by: RobP on April 18, 2016, 09:59:33 PM

OK, I've bled brakes about a million times on various vehicles, including this same bike, but now I am completely stumped with the front brakes on my 1985 K100 RS.  Everything was working fine and I decided to replace the stiff old front brake rubber lines with some braided SS Spiegler lines, along with a set of speed bleeders on the calipers.  After I swapped the parts, I am unable to pump the brakes up to any pressure whatsoever.   When I crack the speed bleeders open I get little 'blips' of fluid indicating some flow, but no real buildup of pressure and no constant, typical flow. I've never used speed bleeders before, so I even re-installed the original bleeders but got the same results.

Any ideas on next steps for troubleshooting?

Some additional notes:

• the Spiegler line between the MC and handlebar stem was too short, so I re-used the existing line again.  Someone had previously replaced this line with  a braided SS line
• I used new banjo bolts and washers from the Spiegler kit on the line above

Title: Re: No Joy After New Front Brake Lines
Post by: Scud on April 18, 2016, 10:05:53 PM

I'm going to assume this is a non-ABS bike - and that the master and all lines were totally dry.

Close your speed bleeders. Take off the master cylinder cover. Squeeze the brake lever, while watching the fluid in the reservoir. If you see some small air bubbles come up, then keep doing this until bubbles stop rising to the surface. Maybe tap the new lines a few times too - to get the fluid to flow down past any trapped air.

Once the bubbles stop coming up, you will have pressure again and can bleed out the remaining air from the lines.

Title: Re: No Joy After New Front Brake Lines
Post by: johnny on April 18, 2016, 10:11:20 PM

could be the piston in the master is pushed back too far and not returning for full stroke... happens frequently when no resistance on lever.. lever just getts pulled too far back... and bam... piston goes back to far and getts stuck... and bam... no pressure... bam...

Title: Re: No Joy After New Front Brake Lines
Post by: TrueAce on April 18, 2016, 10:39:54 PM

Check to make sure you correctly placed the copper crush washers on the steering stem brake pipe. Leaving off a copper washer or 're-using one allows air to enter the system, and you will never bleed it out.

Title: Re: No Joy After New Front Brake Lines
Post by: Chaos on April 18, 2016, 10:42:43 PM

try a vacuum bleeder

Title: Re: No Joy After New Front Brake Lines
Post by: RobP on April 18, 2016, 10:48:43 PM

Scud's reply did the trick - THANK YOU

That, and turning the handlebars to the full left as described in some other posts permitted trapped air to escape out the MC reservoir.

Woo-Hooo!  Back on the road !!!

Title: Re: No Joy After New Front Brake Lines
Post by: Elipten on April 18, 2016, 11:46:29 PM

Yea this is the only vehicle in over 40 years of wrenching to be a royal PITA to bleed the brakes.


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