caliper problem

An eye dropper will work or a small coffee stirring straw utilizing capillary action; the goal is to present the bleeder bore with small droplets. Syringes can be purchased at auto parts stores. You can go to your local pharmacy and buy any size you like, and if this makes you feel a bit squeamish, like the purchase of your first 12 pack of condoms, ask the pharmacists to cut the needle off or back. Syringes are now pretty commonly supplied without needles for oral administration of a number of drugs.

I should have mentioned earlier that when you are in the stage of installing the inner piston fill the bore with brake fluid, wear safety glasses and very slowly and gently push the piston in; good idea to do this procedure on old towels away from painted surfaces. Then install the outer piston, fill its bore, and end cap, plug the bore that communicates with the master and finish off by adding, drop by drop, any additional fluid through the bleed bore. Secure the bleeder valve, and snug the hard pipe; yes it's a PITA, but will save you time over the procedure above if you do this at the assembly stage rather then when the caliper is mounted. This can be messy so when the lines are tight flush with water.

I had one of the first Ducati 750 GTs in '72; the front caliper had no bleeder valve, had to be bled at the line-in junction and left overnight to self bleed. I discovered the magic, or good elf intervention, because I became so frustrated and upset with such a poor design that I had to walk away. I give my GF (soon to become wife V 1.0) a lot of the credit for incentivizing me to abandon the Ducati...the next morning the brake lever was hard enough to remind me of V 1.0's delightful distraction...

Best.

I ordered 3 syringes and 6 needles (14 gauge) 2 inches long for $9 in Florida, due in Monday. Will let you know how it works out.
For your info...needles are measured by gauge, 7 being the biggest and 33 gauge is the smallest.

oh come on every drug addict knows that! ;-)

UPDATE... The syringe and 14 gauge needles showed up and here's how it worked out. Caliper on the bench. Remove the bleeder valve. the needles I ordered are 2" long. I made sure the inboard puck was as protruded as possible. The needle is smaller than the bleeder hole so I hoped that air would escape easily around the needle while I injected the fluid into the caliper. It didn't for some reason. What did work was to dribble fluid into the hole drop by drop and work it with a piece of 1/16 welding rod...in and out, twirl, etc. It took about 15 minutes to fill. Perhaps a long 1/16 drill bit worked by hand would speed the flow. Anyway, the results were very good. Road Scholar has the best idea while assembling.
It seems the standard bleeding method only bleeds the outboard piston and does little or nothing for the inboard. Poor engineering. Even crazier is that I have never read about this in 40 some years.

I have ordered some #10 gauge needles in the hope that I have finally found a way to replace fork oil quickly.

seattle##gs said:

It seems the standard bleeding method only bleeds the outboard piston and does little or nothing for the inboard. Poor engineering.

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The caliper will bleed if the inboard piston isn't pushed back far enough to blank off the drilling.

Does this mean that the caliper must be removed from the fork leg in order to expose the inner piston drilling? GREAT thread.

Scout63 said:

Does this mean that the caliper must be removed from the fork leg in order to expose the inner piston drilling?

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The inner drilling is accessed through the bleed nipple hole in line with the bleed nipple and where it is drilled to the inner piston chamber from. There should be no need to remove the caliper.

When rebuilding, the quickest way is to install the bleed screw, put a bolt in the input port to block it, lay the caliper down so the outer plug is up. Put 1/8" to 1/4" of fluid in the inside side and install the inside piston. Push it most of the way in until fluid starts coming in the port from the outside to bleed screw. Install the outside piston and push it in just enough to uncover the ports. Pour in a little fluid and install the big plug. Install on the bike. Since the caliper is already nearly bled, it will take very little to finish bleeding it.

Edit: Just realized that RoadScholar basically said the same thing quite a few posts ago.

L.A.B. said:

The inner drilling is accessed through the bleed nipple hole in line with the bleed nipple and where it is drilled to the inner piston chamber from. There should be no need to remove the caliper.

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And, if bleeding a dry caliper, it needs to be on the bike or at least in position with the bleed screw upper most.

Some aftermarket Norton caliper pistons have very little chamfer on the inner edge (and no raised centre section) top right.....


...compared to others which, due to the larger chamfer probably don't completely blank off the drilling when pushed all the way in...

marshg246 said:

And, if bleeding a dry caliper, it needs to be on the bike or at least in position with the bleed screw upper most.

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Yes, although I've not had to do that, for the 850 Mk3 at least, (both front and rear calipers) it could be a good idea to 'prime' the caliper in the upright position first, before fitting.

that extra chamfer would make it easier to install the piston.

Thanks L.A.B. (And everyone). I’ve been suffering from a weak front brake.

Well I guess it is surely worth a go. If I take that brake apart once more the fasteners will be worn out and so will I.

Onder said:

oh come on every drug addict knows that! ;-)

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The horses don't .

Is not "horse" street talk for heroin? :-(

So.....the owner put on a magura master cylinder and we bled the brake. I rolled the bike foreward about three times while applying the brake to check how well it stopped and released...so far so good. He drove about a mile and the brake failed to release. Ideas?

more than likely the master cylinder but a small chance the rubber brake hose if it is still in use.

The lever to piston contact point may need some adjustment to insure that the return port isn't being blocked. There should be a bit of free play between the lever and the piston when static.

Best.

seattle##gs said:

He drove about a mile and the brake failed to release

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Did the brake free off after it had cooled down, still wouldn't release or was it dragging?

What eventually happened?