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caliper strip down

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caliper strip down

Posted by martin_champion at July 26. 2017

well I got my hands on a 1976 mk3 that has been dry stored for 20 years , got her running the other day so its time to tackle the brakes, got both master cylinders stripped down but am having trouble getting the screw on caps off the calipers so I can replace the seals and pads,I bought the proper tool !! but it was made from cheese or something and the pins just bent so the rear is off the bike and I have tried putting some heat into it (enough to boil the brake fluid left in the caliper) then tried turning the cap using a adjustable spanner on two roller bearings in the holes but still no joy, any ideas greatly appreciated

Re: caliper strip down

Posted by james_fanning at July 27. 2017

Persevere with the heating up of caliper using the expansion differentials of alloy and steel to break the seal. I put mine in the oven for 15 minutes set at 200 degrees then secure firmly in a vice and apply decent peg spanner. Has never failed to shift end cap. Made my own peg spanner in the end - as you rightly say the ones I've bought of various designs have never been up to it - cutting and shaping a piece of scrap steel to form pegs which fit into a large ring spanner , with a length of GI pipe on the spanner for good measure to provide serious force.

As an aside , eventually I gave up on the original Norton-Lockheed caliper and disc on front brakes of both my MK1A and MK3 850's and fitted Norvil and RGM upgrades which have both produced better front stoppers.


Re: caliper strip down

Posted by christopher_winsby at July 27. 2017

Clean, soak in plus gas for a few days. clean off wrap in oven foil then in the oven on full for half hour. Wear gloves to handle.

You need patience if it has not been stripped before it has over 40 years to corrode in place. Steel and Ally more or less weld them selves together. When heated  holes expand and Ally expands more than Steel.

The other thing is to put a clamp loosely around the caliper and end plate so that when you tun it the tool cannot lift and bend the pegs. You only need it to move enough to break the seal. Then remove clamp and apply more plus gas and let it penetrate or the thread may pick up again.

Re: caliper strip down

Posted by mike_sullivan at July 27. 2017

My exhaust C spanner has 2 holes near the end of the handle appropriately spaced and containing 2 allen headed bolts  to fit the caliper plug; so 2 tools in one, easy to grip & a bit of weight.

I can't take the credit, the caliper tool was out of stack at the time I bought my Commando (20 years ago) & my late father knocked this up.  


Re: caliper strip down

Posted by martin_champion at August 03. 2017

thanks for all the replies and advice , ended up making my own pin spanner out of a couple of old bearing rollers and a length of 25x5 steel, put a lot more heat into them have now got both caps off.

many thanks Martin

Re: caliper strip down

Posted by Julian Wells at August 03. 2017

Now you will have all the fun of trying to get the pistons out of the calliper ...

I gave up and bought an AP caliper and mounting kit from Norvil for my 750's front brake. But what do people do about the MkIII rear brake?

Re: caliper strip down

Posted by james_fanning at August 04. 2017

Luckily original Norton-Lockheed set up on my MK 3 rear brake is still OK following a new master cylinder and refurbed caliper a while ago. Not sure what I'll do if and when pistons show signs of sticking but I've got four spare old calipers in various conditions to play with.

RGM or Norvil , can't remember which , now do caliper pistons with a tapped central hole into which you screw a suitable bolt for drawing out the inner piston.

The AP caliper upgrade kits for front brakes from RGM and Norvil are excellent. Fitted these on both my 850's retaining original refurbed Norton master cylinder in both cases.

Re: caliper strip down

Posted by christopher_winsby at August 04. 2017

I removed my old pistons by using a grease gun and pumping them full of grease. I had previously tried all other methods like an air line but they leaked to much. The grease leaked past the pistons but they eventually came out. Only to disclose that the calipers were in such a bad state I did not risk using them.

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