Gilera Coguar Grimeca brake pistons

roymichaeldea... · L Plate Warrior Joined: 08 Oct 2015 Karma :

Hi

Using the existing brake lever the pistons won't move, am I to assume that they are just stuck...I have new brake piston seals ready to fit....
I am obtaining some Jubilee Clips to wrap around and hopefully extract the pistons without damaging them. I have already left teeth marks on another piston on an XJ600 using pliers....hmmmm

regards

roy

sickpup · Old Timer Joined: 21 Apr 2004 Karma :

Why not just buy a caliper piston puller kit?

bikenut · World Chat Champion Joined: 21 Nov 2011 Karma :

piston pliers yes but are they stuck solid??

don't undo the hydraulics !!!!!!!

remove the caliper and arrange for it to sit in a bucket of hot water.

clamp pistons that you don't want to "exercise" yet, ie deal with on piston at a time. Use a g clamp and wood protection for the alloy and piston etc.......

immerse caliper in hot water straight form the kettle, and gently pump the master cylinder....does the "free" PISTON NOW MOVE ??

DONT PUMP IT ALL THE WAY OUT !!

REMOVE FROM WATER AND LUB WITH FLUID, USE G CLAMP TO PUSH FREE PISTON BACK IN, RPEAT TILL more FREE.

with the master cylinder lid off, you will see a small jet of fluid "fountain " from the small hole nearest the pressure end ( non lever end ) of the m/cyl., yes ??

if no then its blocked, be carefull cos when it clearers a big jet of fluid will come out, staining your cealing :D :D

come back when pistons are you.

make your own piston pliers..... :karma:
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roymichaeldea... · L Plate Warrior Joined: 08 Oct 2015 Karma :

Hi

Thank you for both Great ideas to sort out the brake piston problems

I will try the hot water idea first...

If no success....I will spend the money....and buy the Kit from ebay........as i have several bikes...all old......all need new brake piston seals............the seals are cheap

regards

roy

roymichaeldea... · L Plate Warrior Joined: 08 Oct 2015 Karma :

Hi

I am trying the Hot Water method at the moment

I checked out the Motorcycle Piston Puller Kit...looks good..but...I have several other motorcycles...and the max size in the Kit is 30mm..........the Yamaha XJ600 brake pistons are 38mm approx....

Ideal for the Gilera Coguar...and the Honda Rebel as they have exactly the same brake calipers......

I will keep going.........with the Hot Water

regards

roy

roymichaeldea... · L Plate Warrior Joined: 08 Oct 2015 Karma :

Hi

I have the answer, to removing the stuck pistons.......I have several old bikes so i was looking for a solution not only for this bike but the others as well.....
I thank you for the ideas, I tried, with no success........so finally I bought a Test Pressure machine, used by plumbers to test central heating etc.
I found it tricky to connect a German made Pressure Test Machine to the metric brake caliper but finally managed a connection of sorts, and...magic.......they came out. The Test Pressure Machine goes to 50 bar, over 600psi, i used water in the tank, but, it's been a real problem, how not to damage the pistons. The same front brake caliper is fited to the Honda Rebel 125cc as I have one.....

Happy Days

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

hi,
best method, I have found, for removing stuck brake pistons if hydraulic pressure doesnt work, is with an airline & some ptfe tape.
use air duster & shove tip wrapped with a little ptfe tape into bleed nipple hole & blow out.
if only 1 comes out, use a g-clamp.
just be careful & keep your fingers out of the way!
they can shoot out like a bullet!

cheers,
GAZ

roymichaeldea... · L Plate Warrior Joined: 08 Oct 2015 Karma :

Hi

I did think about using a Compressor, in fact I have an 8 Bar one, but decided against it for the simple reason that i wanted total control of the process, some of my brake calipers have not only 2 pistons but perhaps 3 pistons. And once one piston is pushed completely out you cannot continue. With the Pressure Test Machine, you hand pump the pressure using water pressure.
Someone else suggested using a grease gun with a large handle, i have one but as someone else mentioned, removing the grease from all those different places would be too difficult. and in my opinion, i needed very very high pressure, and the grease gun wasn't sufficient. One old bike I have hasn't moved in 30 years.
I also have a stirrup pump, which goes up to 120psi, but in my opinion, not enough. What is important is have a secure connection between the Test Pressure Machine and the brake caliper....

stirlinggaz · World Chat Champion Joined: 22 Jul 2007 Karma :

Robby · Dirty Old Man Joined: 16 May 2002 Karma :

I'm not sure why you would bother with a pressure testing machine - the master cylinder does the same job for putting pressure into the caliper and pushing out the pistons.

If the pistons are so seized that none of them will move under the pressure from the master cylinder, then the caliper must be totally knackered - or the master cylinder is failing to deliver pressure.

Kickstart · The Oracle Joined: 04 Feb 2002 Karma :

Hi

Not sure I would expect compressed air to push the pistons out if the m/c won't. And with compressed air any piston will come out very quickly (as in able to do a nasty injury).

My compressor manages about 120psi (so about 8 bar). The master cylinder can provide far more than that easily.

All the best

Katy
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