Brakes question

[Jacko]

Hi
My front brake has gone soft.
It has more travel than usual but even stranger it loses all
pressure and the lever comes back to the bar and no braking at all.
squeeze again and back to soft pressure but brakes work.


Going to have a look at weekend but any ideas on where the likely fault is.
ie: master cylinder, calipers, lines,  everywhere??


its a 98 600 with 68K on clock and as far as I know original lines and calipers.


Thanks

[richfzs]

lines on the point of giving up - a (maybe not visibly!) bulge somewhere as you haul on the lever?

I reckon I'd start with new lines

[Skippernick]

:agree

[markbubble]

if your carefull you can clamp the brake line(with proper brake pipe clamp or molegrips wrapped in rag)one at a time and it might help you decide if its the lines or a problem in one caliper,you could check for leaks and do a fluid change/bleed to see if its any better,if you pump the lever does it go better(air in system!)

[FuZzBoM]

I had a 600 and the bakes felt great on that. when i got my 1000 they just didn't feel as good. odd i thought with them being the same calipers. i fitted a set of braided lines and honestly the difference was epic. a set is about £50 off eBay.

When was the fluid last changed? Rough guide is every 2 years i believe but people tend to leave it much longer.

[clayt74]

Make sure it's not a sticky caliper causing ya brake fluid to boil , I had very similar symptoms  except brake seemed ok for first couple of miles then just disappeared.

[Jacko]

it does improve slightly after a couple of pumps.

I'm thinking caliper clean, bleed through / replace fluid.
then lines and ultimately seals in calipers and master cylinder.

in that order, around £100 if it needs the lot i think.

[darrsi]

Does it pulse at all when braking properly?

[blue_faz600]

Brakes, being arguably the most important system on the bike is something I don't mess around with! If there is even the slightest issue, i get it fixed! I did new braided lines and full caliper rebuild with new pads a little while ago and it's not that difficult! The blue spot caliper is so easy to clean and change the seals on, it really isworth doing! The difference is night and day! My bike only had  25k when I did this, so 68k and how many years since manufacture? Most manufacturers recommend replacing lines every 4 yrs anyway! 

Hopefully with that all done, it should cure your issue! If in doubt, rebuild the master cylinder too

[Dave48]

If you look @ your service book/Haynes manual it tells you all you need to know. Original rubber brake lines-replace every 4 yrs OR fit braided -end of problem. Brake master cylinder overhaul kit AND brake calliper seals should be replaced following complete calliper strip & clean. Brake fluid change EVERY 2 YEARS regardless. Think about it  200 odd kgs of bike plus weight of rider coming down from speed to zero under emergency braking-thats a lot of momentum to be converted to heat etc. As said dont take chances with brakes. You should NEVER need to pump lever to get pressure-you wont have time to do this in a "crisis" situation anyway. Have a pal with an old CB 750 Honda & he refused to beleive it was necessary to change his hoses on a 1994 bike- but its his(or someone elses!) life :eek

[Jacko]

Sound advice guys, does anyone have any ideas as to why its ok'ish one minute and gone the next.

My thinking is that there's no point fitting seals and rebuilding if somethings shot and needs replacing.
ie: calliper or master cylinder.

[richfzs]

Sounds like something gave way, if it was really a "its fine its fine, oh fuck its not working" scenario? Have you checked closely for any leaks?

still think hoses most likely though

[Dead Eye]

If pumping returns the pressure then I'd suggest a slow leak? When the fluid is under pressure its leaking out and as that happens the pressure drops and stops the leak. The result is very soft brakes on the first pull, which forces more pressure into the hoses. Second squeeze is much better because the first squeeze has increased the pressure, but the leak is likely back again and you'll notice its soft again if you don't touch the brakes for a while.

An alternative could be the master cylinder - not sure how possible it is, but maybe its busted and is letting fluid back in to the reservoir (failed valve) This would cause exactly the same symptoms as described above but without the leak - or just consider it a "leak" back through to the reservoir

I can't think of anything else off-hand...

[Jacko]

Removed pads today and three out of four fell apart on removal. New pads and a caliper clean up
later and normal braking is resumed. Well on the drive anyway not had chance to take it out.

These were CL A3 pads, albeit well worn, never had a pad have the material and back plate come apart before
let alone three.

So anyway still fancy braided hoses and found these,
http://www.ebay.co.uk/itm/Wezmoto-Yamaha...2714wt_699
/
Look just like HEL or Goodridge or Venhill but cheaper, Anyone any experience?

[Lawrence]

No idea but also interested to know... as far as I'm aware mine are original so I'd like to replace them soon.

[FuZzBoM]

I have fitted the other 3 brands you mention to various machines in the past.. I would say HEL have been my favourite so far for what its worth.

[Andy FZS]

Showing my ignorance maybe.......BUT I would have thought if they fit, don't leak, don't rust (stainless) and don't expand/stretch (braided) then how much difference can there be? I think I may change mine later in the year so will keep an eye on this post.
Cheers Andy

[Jacko]

"BUT I would have thought if they fit, don't leak, don't rust (stainless) and don't expand/stretch (braided) then how much difference can there be?"

My kind of thinking.

Going to be a wee while as I want a couple of days together as I expect that bleeding it all through
is going to be a long drawn out process.

New pads working well and have nice brakes, be interesting to see if hoses make that much difference.

[Dead Eye]

When I did mine (new pads, lines and obviously fluid) I managed to do it in an afternoon - no more than 2 hours I would say? First time I'd ever touched anything to do with brakes so you should be good With bleeding, if it doesn't feel right, just keep going - that seemed to be the case as well as bleeding every joint separately (not just from the bleed nipples, but from the banjos as well )