The International CBX Owners Association

Hi.. I put new Break pads on my 79 cbx and now the front pads are dragging after bleeding out the air. Any suggestions.

Check and Lubricate The Brake Caliper Slider Pins with high temp grease.

If you also changed the fluid.
The master cylinder has 2 ports an intake port and compensating port.
The compensating port is only 1/64 of an inch, if it gets blocked your brakes will drag.
That happened to me after changing the brake fluid.
-Scott

Great advice, spot on.

Also, original brake lines sometimes collapse and act like check valves.If your lines are original its time to change them.

N.

It actually sounds like it's time for a complete brake rebuild.

Dave

That’s never a bad idea with an old bike.

eBay has some SS brake lines, master cylinder, and caliper rebuild kits that replace the old rubber and plastic parts.
Note: if you replace the master cylinder reservoir, the old lid has a steel plate that must be transferred to the new one.
-Scott

Duffey Lake rd. wrote: ↑

Mon Apr 03, 2023 5:17 pm

Check and Lubricate The Brake Caliper Slider Pins with high temp grease.

If you also changed the fluid.
The master cylinder has 2 ports an intake port and compensating port.
The compensating port is only 1/64 of an inch, if it gets blocked your brakes will drag.
That happened to me after changing the brake fluid.
-Scott

Hi Scott

I like the diagram and suggestion but how to unblock the port? Anyone know?

Many thanks

Good stuff, here. However, a suggestion: Jack up the front end to get the wheel off the ground. Apply the brakes and see if they are dragging. If so, place a rag under the fitting at the master cylinder and loosen the fitting. If the brakes release, it is definitely the littl hole in the m/c.

If they do not, then you have either a caliper issue or a hose issue. Then, pull the calipers. if they are both tight on the disc, it's the common feed hose. If only one is tight, it is either that caliper or its hose.Just keep going down the daisy chain. Most likely, it is the m/c. You might be able to try clearing the hole by inserting a fine piece of wire through it. (Something from some 22 gage stranded wire.) Or, just do a rebuilt/new/etc. See notes above.

Some folks in a hurry have been known to push the still dirty caliper pistons back in to the caliper body, along with all brake dust, rust and grime that can gather on the perimeter of the piston, esp. if the dust seal boot is damaged. That alone can cause the brakes to drag, as can corrosion build up in the two channels in which the piston seal and smaller dust seals reside. That has the effect of pushing the seals harder against the piston and preventing smooth retraction of the piston.

If it was me, and you had the time and the $$, I''d be rebuilding the calipers right away if the master cylinder was found not to be the culprit. These brake seals, lines, and hell, even the fluid, could be >40 years old now, so IMHO it's time to show all your brake components a whole lotta' love. Then you can be assured they're right and you'll never have to touch them again.

I would ditch the master cylinder altogether if you are not fussed about concours originality. I fitted an 18 mm Brembo MC off a wrecked Ducati Monster and saw an immediate improvement in feel and performance. Additionally, the extra bleed nipple up on the MC makes regular brake fluid changes and bleeding a doddle. Braided lines, new stainless pistons and seals and dual compound carbon ceramic pads and the brakes are good enuf' to race and better than the AP's you commonly see in the paddock, imo.

Not knowing the size of the m/c of the 79/80 bikes, I can't comment about the affect of an 18mm m/c. However, note that for the 81/82 that would cause a braking effort increase of approx 25% given that the 81/82 m/c is a 16mm (5/8") bore. Just a npte to consider for those who would change their m/c.

granthar wrote: ↑

Sun Sep 03, 2023 10:42 am

Duffey Lake rd. wrote: ↑

Mon Apr 03, 2023 5:17 pm

Check and Lubricate The Brake Caliper Slider Pins with high temp grease.

If you also changed the fluid.
The master cylinder has 2 ports an intake port and compensating port.
The compensating port is only 1/64 of an inch, if it gets blocked your brakes will drag.
That happened to me after changing the brake fluid.
-Scott

Hi Scott

I like the diagram and suggestion but how to unblock the port? Anyone know?

Many thanks

I used a 1/64 drill bit, but I think my port was never drilled at the factory
The whole thing seems a bit wierd, there was a 1/16 hole in the right spot, but it was very shallow.
I had to change the rear rotor because the pads were down to the metal.

Also, if you change the front reservoir, you have to swap the plate between the gasket and lid.
Mine was missing so I had to buy one.

-Scott

Sorry, Larry it may have been 16mm and not 18. Just had that number off the top of my head. It was the same bore as the Prolink mc and had no effect on lever pressure other than much better feel. The carbon ceramic brake pads on the other hand do and only work effectively when really hot so I would not recommend them for street use.

No big thing, Warwick. An 18mm would make things quicker; just a bit heavier at the lever. Didn't want a newbie to go 18 and be surprised. A side note for anyone out there: that prolink m/c is actually 5/8" (.625 ") as opposd to 16mm. How in god's name Honda would go SAE instead of metric is beyond me. Might be, also, for other Honda. I don't know. Just don't try a 16mm reamer to 'clean up the bore'.

Yes, weird change from metrics perhaps because of the US assembly of some models. Sticky calipers are usually dirty calipers in my experience with a buildup of brake dust around the pistons. Disassembly, cleaning, new seals and brake grease will cure unless the pistons are pitted. Grease the pins too including the sliders. Sometimes the hole in the bottom of the mc can be blocked and a wire from a wire brush can be poked thru' to make sure it is clear.

Checking the clearance of the calipers with a feeler gauge when replacing the front wheel is also a good idea, especially if you are not using a fork brace. Or, just pull the ns fork leg out a bit b4 you tighten everything up is normally sufficient.

Replacing the heavy ventilated rotors on Prolinks is also a good idea. As it is unsprung weight it is detrimental to steering. The excess width of the ventilated rotor compared to a normal rotor can be easily taken up by fabricating alloy spacers fitted behind the pistons as has been detailed elsewhere.

For those wanting an original look, David Silver stocks a replica mc but I have also seen CBX's with R1 master cylinders and blue spots and there are a wide variety of options including cast iron rotors for those wanting to improve braking performance. The difference between ordinary brakes and really good brakes is revelatory.