brake problems??

just got an 82 xj750 seca with 4,000 miles on it. rode it around for
about a week and all of a sudden the front wheel is locked up. tried
opening the bleeders and that did nothing. i gather that seca front
breaks are problematic and costly. i'll try to reach the previous
owner and find out if he did anything[ like a rebuild] that could have
gotten parts put on wrong. pads look unworn from what i can see
without taking stuff apart. any ideas???

 

Take the master cylinder cap off and poke a pin or needle through the
tiny air bleeder port in the bottom of the reservoir. That usually
does the trick.

If that doesn't fix the problem, remove the calipers and remove the
dust caps
from the pistons and clean the brake dust from around the piston(s).

If there is only one piston on each caliper, there will be slider pins
that the calipers slide sideways on. The pins have to be lubricated
with a high temperature grease (or a waterproof grease if you ride on
roads that are salted in winter).

If a cursory external cleaning doesn't do the job, you'll need to pump
the pistons out of the calipers by working the brake lever and then
you can clean all the rubber particles and rust out of the brake
piston bores.

 

If the front brake lever is binding or hitting something, keeping it
from fully releasing, pressure will build and cause the brakes to
lock.

One of the less likely causes, happens more often on dirt bikes with
hand guards that just touch the lever when its released, but it
happens now and then.


Dave

 

WD40 will destroy any brake system rubber parts it comes into contact with!

The best solution is to strip, clean and replace seals on the calliper and
use silicone grease to lubricate and prevent corrosion during reassembly, if
your automotive supplier doesn't have silicone grease get it from an
electrical/electronics supplier.

 

the book says use brake fluid to lube. i'll use calipers from my other
seca till i get parts and go with what mark said. pistons and
cylinders have caked on crud from siting so long. btw thanks everyone.
i love this group.

 

All the books say that! Brake fluid is hygroscopic which means that it
readily absorbs water which in the fullness of time causes the crud and
corrosion on exposed alloy parts that were 'lubricated' with brake fluid.
Silicone grease is highly water repellent and is a better lube than fluid,
it won't do any harm to the seals - in fact it protects them and it can be
an effective barrier against brake dust getting between the piston and
calliper bore.

But they're your brakes and its your time spent servicing the brakes again
sooner than you need to.

 

Not in my experience.

 

WD40 is mostly a petroleum distillate with a specific gravity about
the same as diesel. The distillate is supposed to evaporate and leave
the secret proprietary ingredient on the metal part...

WD40 acts as a solvent on rubber parts that are in intimate contact
with metal.

I got tired of the rim corrosion resulting from using liquid soap for
a tire bead lubricant and had a spray can of WD40 handy, so I sprayed
the tire beads and the rim with it.

The tire mounted fine, but the bead was glued to the rim the next time
I changed tires manually, using tire irons.

Another rider confirmed the same experience.

If I had used a tire changing machine to break the beads loose, I
probably would never have noticed anything.

I suppose WD40 would do the same thing to the rubber seals in brake
calipers if the calipers were assembled and then the motorcycle wasn't
ridden for a few months.

 

No argument, just want to mention that I believe DOT 5 fluid is the
exception. Not recommending it as I also believe it needs to be
replaced more frequently.

 

DOT5 has some other disadvantages, like - surprisingly its more compressible
and has a lower temperature rating, but the brake seals do last pretty much
forever.

 

Dunno. I've used it in and around brake and all sorts of other rubber
parts for years, and never had a problem. *Shrug*.

 

And what makes you think that components used in brake systems are
natural rubber?

 

Why don't you tell us what you have experienced and what you have
learned, instead of trolling for a debate?

The synthethic rubber in tires definitely contains an amber-brown
colored oil, it's used to extend the dynamic range of elasticity, and
recyclers got about half to one gallon of oil out of every old tire.

 

What's that got to do with it? Do you really think exactly the same
substance is used for brake components as for tyres? I rather doubt
it.

I'm just saying I've used WD40 for ages to clean brake parts (erm,
except pads....) and I've never suffered a problem. Two posters here
say it will destroy the rubber components used in brake systems. My
own empirical experience, over 30-odd years, says it doesn't. Neither
poster admits to having suffered brake failure from using WD40 around
brake components, so I strongly doubt they have any direct experience.

I'd be interested to know from someone who definitely knows[1],
because if I've been doing something silly and dangerous all these
years, I'd better stop. I'm not trolling for an argument - if anyone
is, you are. I'd really like to know one way or the other.

[1] ie: not you.

 

Well, *so would I*...

Stay out of those hot air balloons then.

Bollocks. Trolling is your whole life.

 

Actually, hot air balloons are the safest form of flight apart from a
modern commercial jet. Way, way safer than private aircraft and
especially helicopters. Fatal accidents are (thankfully) very rare.
Would you like to display more of your ignorance?

Nope. But keep playing.

 

Do you think you will do *anything* useful for your employer today?

 

Oh, I reckon.

 

Well, I know that transmission fluid(FoMoCo) will definitely
compromise brake internals. Don't ask me how I know this. <g>

 

Oh, no! You've made an admission of guilt, at least in the mind of The
Old Gasbag.

There should be a law that states TOG has to mirandize newbies before
he can sodomize them.