Front brake very poor

Hi,

My 1991 45k miles GSX600F front brake is hopeless. It used to be
perfectly adequate but the lever now comes all the way back to the
bar.

I 'think' it got significantly worse after a high-side crash where the
master cylinder got superficially twatted so I assumed I'd shaken some
air into the system. I've bled them on two occasions, but cannot find
any air in there. Is there a special technique?

I've stripped the calipers, cleaned up the pistons and behind the
seals, replaced any deformed seals.

The pads (?type) are ?5 years old but still have ?4mm left. Surely
these are irrelevant though.

It still has the original rubber hoses. Are these the only possible
explanation? Approx hHow much are new hoses?

Anything else I can do to identify the problem?

Steve

 

I'd fit new steel hoses, yes, After 17 years the originals are almost
certainly a bit tired. A complete hose kit for your GSX will be about
£50, I'd guess, and will make a massive improvement.

 

It still has the original rubber hoses. Are these the only possible

Thank you. £50 sounds acceptable. A quick rummage on Google has found
these for £63 + £5 postage.
http://www.bsr-aerotek.com/store/product_info.php?products_id=5042
If anyone knows of a cheaper option then that would be useful.

 

Some dealers keep stocks of the hoses and banjo fittings and will make
them up for you on the spot, for rather less than you'd pay for a
ready-made kit, but for the sake of a few quid, it's only worth doing
if your local dealer is one such, otherwise you could be faffing
around everywhere.

That price you quote seems to be par for the course for a pack.

 

BSR Aerotek make good lines; I use them on my race bike. They
have the added advantage of the "swivelling socket" which means
that you won't kink the lines because they can move freely at
the banjo head. They're also stainless steel, are coated
in clear pvc and you get copper washers too - all plus points
that you may not get in other kits and have to pay extra for.

Once you've fitted the replacement line, be careful that you're
not getting air trapped at the m/c end. This can be a nightmare
to remove if you don't have a bleed nipple at the m/c. Because
air rises in the hoses, if you don't get enough pressure built up
then you can be forever trying to pump the trapped air out but
it just won't budge. There are a couple of ways to sort this:

1. Use a high-pressure/vacuum system like a Mighty-Vac [1]
2. Fit a bleed nipple at the m/c end

I doubt you have air trapped in the lines as this normally only
happens when you have a horizontal run, like in a rear brake line,
and that can be solved by removing the caliper or m/c and making
sure that the bleed nipple is above the m/c to let air flow out
a lot more freely.

On some m/c there is also a bleed screw inside the m/c that if
you frig around with it can stop there being enough pressure to
push the pistons (it's like a return valve) but if you've not
touched that then it shouldn't be at fault.

[1] Some instructions/detail here:
http://www.webbikeworld.com/Motorcy...orcycle-brakes/bleeding-motorcycle-brakes.htm

HTH

 

My local dealer used to do this, but now doesn't - his insurance company
found out he was making up brake lines and refused to cover him (as a
retailer) for the manufacture of any brake components, because of the
liability a failiure of those components may cause.

It would have cost him more to extend the insurance than he ever made
from selling the lines.

 

I recently bought a 3 line HEL kit for my SV650 on ebay for £53-49
delivered. They arrived in 48 hours.

http://stores.ebay.co.uk/Stealth-Bikes

That's the cheapest I've seen braided lines.


--
Lozzo
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X

 

Good Lord.

"Think of the motorcyclists!"

 

Ah, the Mityvac. One of my very favourite tools. I just bought one,
as it happens, one of these:

http://cgi.ebay.com/ebaymotors/Mity...ryZ43989QQihZ008QQitemZ180223621400QQtcZphoto

From the USofA, because it was the cheapest way to do it, even once
the carriage is added. Compared to:

http://cgi.ebay.co.uk/Mityvac-Silve...=item310028736977&_trksid=p3286.c81.m20.l1116

The disparity is apparent, working on two dollars to the pound
sterling.

The basic one is cheaper this way, too:

http://cgi.ebay.com/ebaymotors/Mity...ryZ35625QQihZ008QQitemZ180224205598QQtcZphoto

The UK equivalent being:

http://cgi.ebay.co.uk/Mityvac-One-M...=item190205315891&_trksid=p3286.c81.m20.l1116

[Sorry about the long urls, but I hate the (what seems to have become)
common practice of just posting the item number, as if the poster
assumes that everybody always has an ebay window open - and I don't
much like tinyurl either]

Anyway, comparing the above, it seems that it is possible to obtain
the nicer unit (in metal, with guage) from the States at a similar
price to the basic unit (plastic, no guage) from the UK. So I did.

 

Speaking of which, does anybody know where it's possible to purchase
replacement clear tubing for said device?

 

Local motor factors - windscreen washer tubing. Or your fancy fish
retailer, air pump tubing.

I guess if you wanted something more durable (and expensive) at the
cost of more weight and loss of flexibility, you could go black rubber
from the motor factor or even clear braided petrol piping.

 

I always seem to have loads of those little clear plastic tubes they
supply as breather tubes for batteries. Actually, I converted one at
the weekend to a gearbox oil filler.

 

ahh ha!

It's the clear bit that proved tricky last time i looked, as all I could
find was black rubber tubing.

 

Coo... that must take a while to fill.... thinking about the gloopocity [1]
of gearbox oil and the internal bore diameter of battery breather tubes.

[1] - Well, the K takesSAE80/90 which has the consistancy of treacle.

 

B&Q also do various size tubing by the metre - may be cheaper/easier.

 

That tubing, to borrow a word from my youth, seems a bit 'femmer' to
me. Weak and floppy, to you. Might collapse under vacuum, perhaps.

Ah, there you go, see. Being a car spannerer, I have a small stock of
the filler tubes from pukka gearbox oil bottles, taht I use for
filling gearboxes. Well, I did when you could fill gearboxes -
they're 'sealed for life' now, aren't they?

 

Do they have Bs&Qs in the frozen Midlands?

 

This sounds like my problem. I'm sure there must be air in there that
I just cant get out, as it went from OK to poor following me messing
with the master cylinder.

The article you mentioned suggest some good tips I'll try these before
replacing the hoses.

- To "reverse bleed" you can buy a large syringe (I bought one for two-
strokes at the local motorcycle shop). Partially fill it with brake
fluid, attach it with tubing to the bleed screw, open and depress
GENTLY. This will force most of the air up through the line and out
at the master cylinder/reservoir. Be careful to use foil or rags
around the reservoir as the bubbling air/fluid can splash out. This
step will save you a lot of time if you do it first, then bleed
normally.

- If you can't seem to get rid of the air, try depressing the brake
lever slightly, crack the banjo bolt at the brake reservoir/master
cylinder just enough so fluid begins leaking out, close the banjo and
release the lever. This can get rid of air lurking around the banjo.

- It may seem that no matter what you do, the lever stays spongy. Try
this: With the reservoir lid off, depress the brake lever halfway and
secure it with a Velcro tie, a zip tie, tape or whatever. Leave it
overnight. In the morning put the cap back on, take off the tie, put
push the bike and pump the lever a couple of times...if you're in luck
it will firm up."

Cheers for all the help
Steve

 

Your local motor parts shop

--
Lozzo
Suzuki SV650S K5
Honda CBR600 FW trackbike
Yamaha SR250 Spazz-Trakka
Suzuki GSXR750 L
Suzuki TS50X
Suzuki TS50X