Caliper inner piston removal.......

[JOHNO23]

I’m currently rebuilding my mk3. I am keeping the rear brake set up as it is,but I want to fit new seals in the caliper.
I have removed the outer piston but cannot remove the inner one . How do you guys Normally do this?
It’s a bit of a pain in the arse.............. Any help much appreciated.......

 

[L.A.B.]

Used compressed air if you have it, at the bleed port with the outer piston drilling plugged with a pencil point, pointed tool, etc.

Rebuild a Norton Commando Disc Brake Caliper - Motorcycle Classics

Rebuild and update Norton Commando disc brake calipers.

www.motorcycleclassics.com

When fitting the inner piston, do not push it all the way in. Insert only as far as necessary to fit the brake pad.

 

[cliffa]

This is the way I do it..

front caliper

I am working on a front caliper which seems to have seized up long ago. Neither puck responds to compressed air. It is now soaking in penetrating oil. I would like to apply some heat so what temp can I safely use?

www.accessnorton.com

If it proves even more stubborn, heat up the caliper again then smack it down on a piece of 3/4" ply or chipboard on a solid concrete floor and it will start to move out.

Once you have it out clear the three passageways with a drill bit. I opened mine up to around 3 mm, but be careful not to go too far with the cross drilling otherwise you'll end up with an air pocket which cannot be bled.

Cheers,

cliffa.

 

[dynodave]

See my disassembly pix here: https://www.accessnorton.com/NortonCommando/commando-caliper-dismantle.30819/

Lab send us to this Interesting article...after the 8th pix is written:
" The inner piston is a little harder to remove. Stuff the bore with a rag to act as a cushion. Plug the transfer port to the rear piston with your finger. Using compressed air and a blow tip, apply air pressure at the line fitting in short bursts, easing the piston out slowly so it doesn't pop out suddenly and hit your finger. "

This is an example of a caliper piston almost ready to "fall out"/"fall apart"

If it can be dismantled with only 150psi air than it is not stuck in any significant way, They on occasion require as much as 1500psi of hydraulic push. But all passages must be cleaned before hand or they will split around 2500ps.
Automotive brakes can run at 1500psi.

Once you have it out clear the three passageways with a drill bit. I opened mine up to around 4 mm,

You do not have to "drill it" (remove metal) any at all.
As I have stated a #31 drill as a finger driven scraper will tell you if the passages are clear.

 

[Sport75073]

I just went through this last week. Inside piston wouldn't respond to air, heat, penetrating oil, or smacking it on a hard surface. Finally, I put in a new outboard piston and seal, buttoned it up, and reconnected it to the master. I put an old brake pad to the outside piston and used a wood shim to prevent it from moving inward. As I pumped the master, the inside piston began to move. When it popped free of the seal, I disassembled the rest and was, with a little cleaning, able to get the inside piston out. HTH

 

[L.A.B.]

Lab send us to this Interesting article...after the 8th pix is written:
" The inner piston is a little harder to remove. Stuff the bore with a rag to act as a cushion. Plug the transfer port to the rear piston with your finger. Using compressed air and a blow tip, apply air pressure at the line fitting in short bursts, easing the piston out slowly so it doesn't pop out suddenly and hit your finger. "

This is an example of a caliper piston almost ready to "fall out"/"fall apart"

If it can be dismantled with only 150psi air than it is not stuck in any significant way,

Not all pistons are going to be "stuck" and there was nothing to suggest the piston in this instance was stuck, only the desire to change the piston seals. "150 psi" where the piston isn't stuck is more than is necessary.

 

[cliffa]

You do not have to "drill it" (remove metal) any at all.
As I have stated a #31 drill as a finger driven scraper will tell you if the passages are clear.

Agreed, you don't have to. I cleared mine that way, but then I looked at the connections and they were larger so I opened mine up a bit (actually to 3mm) and have zero problems bleeding my brake since. Additionally if you run the drill bit a tiny bit further in on the back ( like 3/32"), it will help stop the piston blocking the passage if pushed fully home.

 

[htown16]

If you are using air pressure, a plastic golf tee works well to block the transfer port. Hold it in place with a screwdriver. Keep fingers well away. Don't shake hands with danger.

 

[kommando]

I use an oil can to apply pressure, makes a mess but the piston comes out less abruptly.

 

[DevonNorton]

This shows a modified piston with a threaded boss for use as the inner piston. Makes the job a lot easier.

Available from the Norton Owners Club spares catalogue.

I have one of these fitted to my 1972 Roadster. It works fine and is easy to remove.

Andy

 

[JOHNO23]

thanks guys, I don’t have access to compressed air,so I will try to heat it and bang it out which I’m not that confident about. Perhaps I’ll have to find an engineer shop to do it for me......

 

[cliffa]

thanks guys, I don’t have access to compressed air,so I will try to heat it and bang it out which I’m not that confident about. Perhaps I’ll have to find an engineer shop to do it for me......

It should be fine as long as you keep the impact to the closed end of the caliper. Get it nice and hot and wear a suede glove. I dribbled brake fluid around the piston as well ( it's a very good rubber lube).

 

[Torontonian]

Yes just lube it up , smack it hot , down on a piece of wood using gloves It'l move and you can play cave man as the wife watches , all concerned. All Norton Owners should have heavy leather gloves.

 

[rweb]

thanks guys, I don’t have access to compressed air,so I will try to heat it and bang it out which I’m not that confident about. Perhaps I’ll have to find an engineer shop to do it for me......

Just did mine last month. First rebuilt the M/C and bleed the line. Use the master cylinder to push the pistons out. After moving both pistons out and pushing them back a time or two clamp or shim the outer one back in and use the M/C pressure to push the inner one out. Remove the outer cap, piston and seal to let the inner piston to fall out. Check the grooves for corrosion deposits, mine had a good bit of crud at the bottom of the grooves.

 

[dynodave]

Check the grooves for corrosion deposits, mine had a good bit of crud at the bottom of the grooves.

Both aluminum and iron in nature want to live in their oxide ore state = iron/steel rust or white aluminum oxide both are aided by water suspended in hydroscopic brake fluid..
Pure iron/steel or aluminum is in terms of human eternity only a temporary situatiion. Crud is the normal state LOL as is rust even if powder coated....LOL
Back to regulaar programming....

 

[Torontonian]

Both aluminum and iron in nature want to live in their oxide ore state = iron/steel rust or white aluminum oxide both are aided by water suspended in hydroscopic brake fluid..
Pure iron/steel or aluminum is in terms of human eternity only a temporary situatiion. Crud is the normal state LOL as is rust even if powder coated....LOL
Back to regulaar programming....

Just get brutal.

 

[oldmikew]

Measure the piston id and get tap that will cut a thread.. screw itinto bottom of piston and then secure tap in vice and judicious striking of caliper body will free ,