This is a bit OT, but falls well within our usual engineering parameters.
I've stripped the RH front brake calliper off my 1983 Honda VF750. It has
been standing for ten years & the twin pistons are well and truly stuck.
They are, of course, hard chrome plated & I cannot grip them in pliers too
hard. They live in an aluminium calliper body.
I've tried pouring boiling water over the calliper & filling the hollow
pistons with cold water without any effect.
Because of the nature of the rubber seals on the piston, I'm loath to use my
normal tipple of PlusGas in case it makes them swell up even more.
Any ideas, gentlemen?
AND - does anyone have a working RH calliper for above they can sell me?
Kim, you might try applying compressed air to the brake line pasage. Wrap a
stout cloth around the caliper to catch the pistons. To apply more force you
could fit a zirt fitting and push them out with a grease gun.
I never like using compressed air for this sort of thing. Air is
compressible, so energy gets stored, so energy gets released when the
pressure is released - your piston may well come free, but it's also
likely to fly across the workshop.
I'd much rather do it with hydraulic pressure (and no air bubbles). It
can generate even more force (unlikely that you need it) but when it
blows free, it's much more controlled. An old master cylinder and a
spare flexy are worth hanging onto..
if you can make an adapter to the fitting on the caliper, do so. then
install a grease fitting and use a high pressure grease gun.
be sure to clean the grease after it comes apart, naturally.
i've used this a few times.
good luck, sammmm
for a brand new genuine Honda one.
Non-genuine ones may be available elsewhere on the site.
It may be cheaper to ride the bike more often ;-)
I've no room to talk. 1978 750F2, 13,000 miles from new.
I had a problem with my calliper pistons pitting. They are now stainless
steel. A bit softer than chrome but they will never corrode and, as you can
see, they don't get that much use.
As SAMM says replace your brake feed with a grease nipple and pump in grease
and leave for a while then pump in some more.
Its usal to use thois method when restoring old cars etc.
Kim Siddorn wrote:
Soaking it in Coca-Cola worked. Both pistons came out last evening & all I
need now is a set of seals.
Thanks to all for their most welcome advice, especially to Gary Millward who
was kind enough to go out of his way to drop into his local bike breakers
Thanks Gary, I owe you a pint!
J. Kim Siddorn,