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???

 

zoot wrote:

Did any fluid come out when you opened the bleeder screws?  A very common
cause of brakes locking up is a blocked fluid return port in the master
cylinder.  Another possibility is one or both calipers are stuck on their
sliding pins or that the pistons are frozen in the caliper bores.

On a bike that old, with so few miles, it's a pretty sure thing it's been
sitting unused for years.  I would take the calipers and the master
cylinder apart, clean and inspect them and replace the seals and all rubber
parts as necessary.  I would also replace the 27 year old rubber brake
lines with braided stainless steel covered lines.

--
'07 FJR13AW  '99 EX250-F13
OMF #7

 


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.

 

zoot wrote:

More amusing<for me anyway> story then useful info at this stage. Picked
up a very used, very tired, 1978 CX500. Front disk was so badly locked
up we couldn't load it in the truck. Guy who sold it to me pulls up a
big stick and starts whacking the wheel cylinder with it like it owed
him money! ~15 seconds later brake was loose and we rolled it on the truck.

The pads are self adjusting and not stable. Park it and a couple of
rain/dry cycles will cause them to swell and if it has a 'rust ring'
that prevents the pads from backing off properly you get stuck. If it
was me I would maybe put some WD40 on the wheel cylinders and do the
whack-a-mole thing to see if that helps. *IF* it does, you probably
should service the brakes as the pads could be the originals and you
need to clean the wheel cylinder.

Rick

 



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.