Brakes Too Stiff

[Milan]

Got a bike the other day that had an aftermarket or Non OEM front master cylinder on it.

You just touched the level and it was done breaking.
Thought it was the volume of the master that was pushing to much fluid.

Replaced it with a stock RD400 one, and still does the same thing


Wondering if the PO put on too thick of pads and they are too tight.
Its a Daytona, so I think the front discs are thicker.

Was going to take it apart tonite.

Any theories?

M

[paul1478]

when I first got my bike the rear would do that. nothing to locking up.
when I tried to take the caliper apart the pistons were rusted. I replaced them and all good. So, while you have it apart be sure you pistons are moving in and out and are not partly froze.
good luck.

[SoCal250]

If it still has the 2V0 calipers and rotors on it, they are different than the standard RD400 (I'm sure you knew that). Daytona rotors are thinner (5mm vs. 7mm). And Daytona pads are totally different because it's a single piston caliper.  They are different shape and thicker than regular RD400, and the pad surface is angled opposite of each other due the swinging arc of the caliper as the brake is applied.

Make sure the pads are installed correctly and that the caliper unit rotates freely on the mounting/guide sleeve. Unbolt the caliper and confirm that the piston is moving as it should. Might be time to disassemble and check for a piston issue like Paul mentioned.

[Milan]

The bike had drilled front & rear rotors.
So the shop that did it, had to do something in there

Hard to see why they let it go out with the brakes like this.

But, nothing seems to surprise me anymore on what people do.
I could start a good rant.........

First time taking these apart, so some learning.
( I have done cars prior tho )


M

[m in sc]

pad and rotor thickness will have zero to do with master to caliper ratio, (lever feel) just fyi. but def check the sliders and pistons as paul suggests. I would venture the bore on the master is too large if all that is free moving.

[Milan]

I replaced the Master with a Stock RD one.
Did not help.

M

[m in sc]

what year?

[Milan]

1979 Daytona USA.

Took piston out & it was rough.
Ordered a new one + seal kit from HVC.

M

[pidjones]

I would also check the lines for obstructions/cinks/failing that could block flow. I had a GL1000 once with no movement on one caliper. Discovered the banjo bolt was a solid bolt with no holes!

[Striker1423]

I would also check the lines for obstructions/cinks/failing that could block flow. I had a GL1000 once with no movement on one caliper. Discovered the banjo bolt was a solid bolt with no holes!

Haha, that's just ridiculous.

[m in sc]

yeah thats very possible. i would def replace the lines anyway.

[pidjones]

Yes, it's happened. I use the bolt now for a blank-off when pumping pistons out with a grease gun.