Front brake XS650 1975 and 1978

[Niels B]

So i have now 4 running XS 650ties, two '75 and two '78 models. (I know it's too many and i will soon thin out a bit ) need room for new projects and can't ride them all anyway.
However one of each have weak front brakes - they all run with original brake system and all have new pads, do not recall any longer where i got them. They all have firm non sponge grip, however two are not braking anywhere near the other two, should i try to find different brake pads ? replace the disk ? any idea ? haven't done anything different with the two with weak brakes, but i don't feel safe riding them if they don't have better stopping power. I'm kind of staying to the original look so not to kean on replace with setup that do not match.

 

[motormike]

The caliper slides on a sleeve.... sometimes the sleeve is contaminated, and it makes the caliper stick and not brake evenly. Photo shows stock rubber sleeve new and one that has been covered with fork oil... this causes the sleeve and other brake rubber pasts to deform... swell... I'd start there... You can pull the caliper off.... gently press the brake lever,, release.. does the piston retract..? possibly the piston is sticking... ?

 

[gggGary]

for the 78,
the 75, with two pistons may have one stuck piston.

 

[Niels B]

The caliper slides on a sleeve.... sometimes the sleeve is contaminated, and it makes the caliper stick and not brake evenly. Photo shows stock rubber sleeve new and one that has been covered with fork oil... this causes the sleeve and other brake rubber pasts to deform... swell... I'd start there... You can pull the caliper off.... gently press the brake lever,, release.. does the piston retract..? possibly the piston is sticking... ?

I’ll take a look at that thanks

 

[willis]

How are your brake lines? Still running original rubber? If so there could be collapsing lines.

 

[Niels B]

I’m running rubber but they are new - should probably have gone with stainless steel line. I renewed all but the disc - wonder if the pad or the disc could be the reason. Discs are old for sure !

 

[Dom]

My 75 is the same, I've replaced all lines with braided, overhauled the mc and caliper. Having drilled the disc as well I can only think it must be the pads even though they have loads of meat on them, they blacken the disc rather than scrub it clean.

 

[Wingedwheel]

Originality aside, I found a noticeable improvement going to braided lines. Did you use any kits in the MC’s? The shorter piston in the kits that are sold now have given me a few “issues”. You can buy an OEM but at the cost it’s better to upgrade the MC.

 

[Niels B]

I bought what was needed ( kits from MikesXS ) to overhaul the MC and Caliper, also new pads. I even tried a complete new replica of the original caliber on the ‘75. Didn’t make a difference. Only thing I haven’t tried is replace disc and braided line. Looks like I have to give that a try. While it’s all off I can once again make sure all moving parts are moving freely :-(. One thing is for sure no ride in traffic until it brakes perfectly . Even with drum brake on the back that works - they don’t do much alone . Have a 45 chin HD flathead from the 40ties drum front and back - not a lot of braking power there - rode one of those around for years all over Europe in the 80ties - not sure how I survived that - younger and dumper I guess

 

[gggGary]

Very common for pads to get contaminated with fork oil from a leaking seal.
There is NO cure for pads that have been oiled.
On the odd chance you have a glazed rotor they can easily be sanded.
A fine flap disk (320) on a grinder applied to a spinning rotor results in a beautiful finish.

 

[40north]

it has happened to me that silicone (DOT 5? or spray-lube?) contaminated a front disk/pad set. Makes a dramatic experience to discover!

Best!

 

[jetmechmarty]

Two Specials, one stops, the other, sort-of. 2nd bike also had a squeal. I set out to replace the pads. What I found were Sumitomo (OE) that looked like new. On a flat surface, I ran the face of each pad on 320 garnet paper. I carefully cleaned the caliper with brake cleaner. Where the metal parts of the caliper slide on one another, I placed a dab of white lithium grease. I reassembled and tested. Success! I took the bike to Arkansas and the brake worked great all weekend. YMMV