Topic: CB750 K2 brake caliper problem.

[olasek18_18@o2.pl]

CB750 K2 brake caliper problem.
Reconditioned caliper, cleaned, new bleeder valve.
Unfortunately, after bleeding, when the brake gets hard, after waiting a few hours, the caliper body in the place of the bleeding valve leaking.
I used a special cleaning material, polished the contact point of the vent valve and caliper bodu, unfortunately it does not help ...
 do you have any ways to seal it?
I don't want to tighten too much so as not to damage the thread.

[CycleRanger]

Compare the taper of the new bleeder screw to the old one and make sure they are the same.
Some after market screws aren't cut at exactly the correct angle.

[BenelliSEI]

Very frustrating, after all you’ve done. There can be a few causes.

1. The seat area is cracked or damaged. Only careful inspection will reveal. The only way to repair is with a drill bit with similar seat angle and touch up the seat........ lock the bit in a tap handle and do it by hand!
2. I’ve bought some replacement bleed nipples that are just JUNK. They don’t have enough reach length on the shank, below the threaded portion, to actually engage the seat enough (see my crappy drawing). The threads bottom, before the tip really engages the hole. Compare the new one to your old part, it will be obvious.
3. As suggested above, they may also have too flat a taper to engage properly. Sometimes, they are made so poorly, I’ve had to dress the tip with a file while turning them slowly  in my drill press or lathe.

[Nurse Julie]

Agree with the above. If the taper below the thread is too short, it won't function properly.

[olasek18_18@o2.pl]

I compared the angle of the cone of screw and the length of the screw, they are the same...
I tried to polish the cone surfaces with polishing compound but that didn't help either.
Perhaps there is a deeper crack...

[BenelliSEI]

I compared the angle of the cone of screw and the length of the screw, they are the same...
I tried to polish the cone surfaces with polishing compound but that didn't help either.
Perhaps there is a deeper crack...

The length of the part that is critical is how far it sticks out below the threaded portion, the “reach”.
You can try and recut the seat as I described. Good luck!

[CycleRanger]

You can also use a bit of teflon tape on the screw, sometimes that's enough.

[bryanj]

They can be done up pretty tight without any damage

[PeWe]

This is not a pipe thread....
Check for old dried brake fluid blocking the thread. That sit rather hard, like Loctite glue.

[dave500]

its not a tapered thread PeWe,as cycle ranger says try teflon tape,i use it anyway on bleeders on anything,that way when i use a vacuum bleeder false air bubbles arent shown in the bleeder tube.

[PeWe]

OK, I remembered wrong.
M10 fine thread then?

I have refreshened the bleeder threads in one caliper with old  hard residues.
I was happy that I had a tap.

[BenelliSEI]

I compared the angle of the cone of screw and the length of the screw, they are the same...
I tried to polish the cone surfaces with polishing compound but that didn't help either.
Perhaps there is a deeper crack...

So if the cone (tip of the new bleed nipple)  is engaged correctly in the seat of the bore, then the problem is in the caliper. You should be able to see it with a bright light and magnifying glass? Using the correct size, numbered drills open up the hole by the tiniest  increment possible and reface the “seat” with a larger bit. Fit the bits to a tap handle and do this by hand.

P.S. Tapes or thread sealers on a high pressure fitting are ultimately not going to cover a problem.

[MauiK3]

I had this happen with my K3 750, I used new calipers with stainless steel bleeders. One weeped after it sat. I was lucky, a few times removing it and checking and re-tightening cured it. I still don't know what it was but it is ok now.
Here in Hawaii, when we don't know or can't explain something we say it's the Menehune's fault.
Menehunes are the Hawaiian version of elf.
Melekalikimaka to all