how much brake lever travel should i have r80/7?

[Northern Monkey]

i have a 78 r80/7 using cable operated master cylinder - ive been trying for days to 'bleed' the system to get a really firm brake lever. the lever is tight but i can pull it back to the bar and it feels as though brakes are really on but should i be able to pull all the way back to the bar? cheers

 

[JJH]

Obiousley not all the way to the bar. A lot of people put a bar mounted master cylinder on. There could be something going on with the cable. Of course the hoses themselves could need replacing. Jjh

 

[Northern Monkey]

Thanks it's had new hoses and cable so I'm 'fairly confident' they're OK - the calipers are working and not showing any leaks - however when brake is applied there are some fine bubbles appearing in the reservoir - I'm thinking the master cylinder may be leaking in air past parts Ltd are quoting £60 ish to refurb it - so unless there's anything obvious I'm missing I'll do the usual and throw money at it!!!


Sent by magic

 

[JJH]

Is there a bleed nipple at the master cylinder? If not pump brake lever a few times and open union slightly to see if there is any air trapped there. Tighten while still holding lever. Hope it works. Any other work done? New pads? Are they seated correctly. Make sure a slightly misplaced shim or spring is not pushing pads out. Jjh

 

[Northern Monkey]

No new pads- no nipple on master cylinder - which Union are you referring to??


Sent by magic

 

[AberdeenAngus]

Try loosening the reservoir lid, tie down the lever, and leave overnight.

 

[Northern Monkey]

Now that's a new one on me! Will give that a blast cheers


Sent by magic

 

[Box’a’bits]

Undo the jubilee clamp, tilt the master cylinder so that any trapped air bubbles can rise, have another go at bleeding. While it's clamped down, the air sits above the m/c, & can only be forced down into the brakes.

 

[Northern Monkey]

Thanks for that, no wonder I'm failing!


Sent by magic

 

[Beemerboff]

Sometimes bleeding just doesnt seem to work - I think air gets drawn in past the threads on the bleed nipple.
Speedbleeder nipples have a sealant on the threads and have always worked for me, but Teflon tape might work .
Your undertanks MC must be getting long in the tooth too and might be drawing air, and the calipers too - It is possible for the calipers to draw air without a noticeable leak, but any sign of wetness at the seals is a pointer on either.

 

[Kenny]

Let's be quite honest, these particular brakes are utter crap.....even with well set up ones the lever can be pulled hard back but as explained in the original post, the brakes are well biting by then. Usually lever pulled/tied back works better with handlebar mounted cylinder but well worth trying. Last time I couldn't get that last bit of air out..I used a large syringe and sucked the life /fluid through the nipple, that worked

 

[AberdeenAngus]

£30 will buy you a vacuum brake bleeder. That should sort you out.