Bleedin' Brakes
 

Sorry to dredge up what should be another simple topic and questions that have been asked a 1000 times before i know and yes i have searched topics but i have exhausted all the options i think.

As you may not know, the bike was left standing for a few years and i am still rebuilding it and have left what i thought would be the easiest job until last. Oh how wrong was I and i have never had problems like it before!

Part of this meant the calipers had to be stripped & cleaned. When i rebuilt them i purchased new OEM pistons and seals (dust and main seal groove was also cleaned out) and they were rebuilt with red grease. Caliper slides & boots were cleaned up and re-greased with silicone grease.

New stainless nipples have been put in and belt and braces, the thread was wrapped in some PTFE.

New stainless lines have been put in - 3 line set up so the original splitter is still in place.

Master cylinder has been rebuilt using a kit and the inside bore is smooth and the tiny return valve hole has been checked to make sure it is clear.

No matter how i bleed, i can't seem to get the lever hard.

I have tried bleeding the traditional way - pull lever, open nipple, let fluid come out, close nipple, release lever - repeat until no more air bubbles come out.

I have tried reverse bleeding from the nipples with a syringe

I have tried reverse bleeding from the nipples with and Gunson Easibleed pressurised from a tyre.

I have cracked all the banjo's to make sure there was no air hiding anywhere here, whilst using the lever method.

I have tied the lever back to the bar overnight with the top loosely on the reservoir

I have taken the calipers off and pushed back and pumped back out the pistons separately in case their was an air pocket behind the pistons.

Tried all the above with the bike on an Abba so it was level and then on the side stand and making sure the MC was at the highest point.

The brakes do seem to apply when i use the lever and release when i let go, it's just the lever is not firm and very easily pulls all the way back to the bar, no matter what i do i just can't seem to get any pressure built up?

Any ideas as to what i may have missed please as i thought i had all bases covered and with all new parts, i wouldn't have thought i would of had these issues and have never been caught out like this with brake bleeding in the past.

Thx

Re: Bleedin' Brakes
 

pads take a while to settle into the discs and until then the lever will feel a we bit spongy. bed the pads in for about 100 miles of so then do another quick bleed.

best bleeding is done with a "tube and jar" put brake fluid in jar about 1/4 full then immerse tube end in brake fluid then attach tube to nipple, open nipple and pump the brake lever till the brake fluid fills the tube and watch for bubbles. if no bubbles then on the pull stroke close the nipple then let go of the lever. no need for "open close" of nipple while pumping.

sometimes you need to tap the brake lines repeatedly with a spanner of something while bleeding, this dislodges any clinging air bubbles.

Re: Bleedin' Brakes
 

Thanks Bibio - that makes sense. i will give that a whirl next.

yes, sorry I've been through so many things i forgot to mention i have tried tapping the brake lines whilst bleeding as well.

The only thing is that i was hoping to get the bike in for an MOT and the way it is now i am worried about the "excessive travel" fail. The lever adjuster is already on 1 and the lever pulls with no resistance to about 1cm from the grip and then only then can you feel the lever harden slightly.

There is obviously pressure in there as one of the discs you can actually see flexing under the pressure from the pads when the lever is pulled.

Re: Bleedin' Brakes
 

as long as it has enough power on the rolling road scale then thats all the tester is looking for.

i have stripped down some shocking braking systems that have passed an mot.

Re: Bleedin' Brakes
 

This is usually a sign of a sub-par Master Cylinder.You should be able to bleed the front brakes on a Motorcycle in minutes without any fancy gizmos.

I've never had much luck with,"Rebuild" kits so now I just bite-the-bullet and buy a new MC when this happens.

Re: Bleedin' Brakes
 

i think your are right R1ffr4ff, I thought there was enough braking power there but took the bike out for a spin and needless to say, there was really no bite there.

While i was out i detoured to the MOT place and the chap there said try another MC as well as i have tried everything else possible - So it looks like i will be ordering another MC. Not due to arrive until the end of the week but will let you know how i get on.

Re: Bleedin' Brakes
 

Which ones did you buy if you don't mind me asking?

Re: Bleedin' Brakes
 

nowt wrong with MC rebuild kits as long as you get the OEM ones. robinsons have them on promotion right now for £9.68 59600-45860. yes that right £9.68 for an OEM kit.

Re: Bleedin' Brakes
 

Jees! Cost me best part of £50 for OEM rear master kit...what gives??

Re: Bleedin' Brakes
 

its the front one and its on promotion... the promotion might end tonight or tomorrow.. who knows so best get it while you can.