hogtyed
Paul
My ‘79 keeps having the front disc sticking. I till have the stock 2-piece brake line installed. Is this the most likely root of the problem?
-
Enjoy XS650.com? Consider making a donation to help support the site.
XS650.com receives a small share of sales from some links on this page, but direct donations have a much greater impact on keeping this site going.
Disc brake sticking
- Thread starter hogtyed
- Start date
It is probably something else.
Check that the caliper piston is moving freely, when they get caked in brake dust and grime they can stick.
Check that the pressure relief hole in the master cylinder is not blocked.
Give the whole system a good clean inside and out and see how you get on.
Check that the caliper piston is moving freely, when they get caked in brake dust and grime they can stick.
Check that the pressure relief hole in the master cylinder is not blocked.
Give the whole system a good clean inside and out and see how you get on.
I vote for old hoses. Quite often the hose will start to separate on the inside . The brake fluid can go to the caliper but becomes slow to return on the release. Sometimes it can completely block the return and cause caliper lockup. A partial lockup will cause overheating of the rotor. I think it is time for a SS one piece line.
tim
tim
The front brake line may not be your issue now, but it should be replaced. Most rubber parts have a rather short life expectancy, About 5 to 10 years.
Brake lines are one of these items. They may look ok on the outside, but rot from the inside. I wouldn't run them much over 10 years old.
The one piece braided stainless steel lines can be gotten for not much money but work very well and seldom give issues.
From my experience sticky disc brakes is most often from a plugged pressure relief hole in the master cylinder or the pin the caliper slides on.
The caliper has a rubber boot that allows it to slide on a steel tube, held in place by a bolt. As the rubber ages it gets hard and can swell. Either can bind the brakes.
Crud build up between the rubber and pin is another.
As the bike sets there, reach down and try to move the caliper. You should be able to move it a small amount . If it won't then you need to inspect bushing. While in there check for a torn or rotted dust seal around the piston. This seal keeps out dust, of course, but also water. Water can cause rust. The chromed steel piston is rust resistant but it can fight it for ever.
There are several good "How To" threads on here.
Leo
Brake lines are one of these items. They may look ok on the outside, but rot from the inside. I wouldn't run them much over 10 years old.
The one piece braided stainless steel lines can be gotten for not much money but work very well and seldom give issues.
From my experience sticky disc brakes is most often from a plugged pressure relief hole in the master cylinder or the pin the caliper slides on.
The caliper has a rubber boot that allows it to slide on a steel tube, held in place by a bolt. As the rubber ages it gets hard and can swell. Either can bind the brakes.
Crud build up between the rubber and pin is another.
As the bike sets there, reach down and try to move the caliper. You should be able to move it a small amount . If it won't then you need to inspect bushing. While in there check for a torn or rotted dust seal around the piston. This seal keeps out dust, of course, but also water. Water can cause rust. The chromed steel piston is rust resistant but it can fight it for ever.
There are several good "How To" threads on here.
Leo
Last edited by a moderator:
Don't try try to play "guess the bad part" on front brakes.
It really is simplest to buy a new one piece brake line and do a full overhaul. There are great how to's on the whole process in tech thanks to recycle bill.
Often no parts needed for the MC, caliper piston will always have "some rust pitting". caliper rubber condition depends on how bad the fork oil leaks were. Fork oil destroys brake rubber parts making them fat, soft and gooey.
I'll toss this in here;
I just replaced the upper hose on madness, a late model dual caliper conversion. The "braided steel" hose was too long after chooper handlebars were tossed. I emptied the reservoir and drained some fluid from one caliper bleeder then changed to a shorter hose.
Here's the "experiment"; Bike on lift doing rewiring, so I wasn't in a hurry.
I did NOT bleed the brakes! I merely arranged all parts to assure a completely uphill path from caliper to MC reservoir.
On the side stand, bars turned full left, will often get this, on specials with the angled MC you might have to rotate the handlebars in the clamps.
Fill the reservoir after the set up, so fluid doesn't run out a corner (the reservoir will be slightly tilted). Slowly pump the lever, off and on over a couple days. Put the cap in place between pump sessions so the fluid doesn't absorb moisture. At each lever release an air bubble escapes the bleed port. You cannot rush this, as the air takes some time to migrate via gravity from the lines up to the MC bore. Probably a 100 squeezes in all over three or four days, and it's 100% bled, hard lever. Not sure if it was more laziness or to prove a point, but it worked! Even if you bleed there are always a few small air bubbles "hanging around" this can be done cover on, occasionally after any brake work to achieve and maintain a hard brake lever.
It really is simplest to buy a new one piece brake line and do a full overhaul. There are great how to's on the whole process in tech thanks to recycle bill.
Often no parts needed for the MC, caliper piston will always have "some rust pitting". caliper rubber condition depends on how bad the fork oil leaks were. Fork oil destroys brake rubber parts making them fat, soft and gooey.
I'll toss this in here;
I just replaced the upper hose on madness, a late model dual caliper conversion. The "braided steel" hose was too long after chooper handlebars were tossed. I emptied the reservoir and drained some fluid from one caliper bleeder then changed to a shorter hose.
Here's the "experiment"; Bike on lift doing rewiring, so I wasn't in a hurry.
I did NOT bleed the brakes! I merely arranged all parts to assure a completely uphill path from caliper to MC reservoir.
On the side stand, bars turned full left, will often get this, on specials with the angled MC you might have to rotate the handlebars in the clamps.
Fill the reservoir after the set up, so fluid doesn't run out a corner (the reservoir will be slightly tilted). Slowly pump the lever, off and on over a couple days. Put the cap in place between pump sessions so the fluid doesn't absorb moisture. At each lever release an air bubble escapes the bleed port. You cannot rush this, as the air takes some time to migrate via gravity from the lines up to the MC bore. Probably a 100 squeezes in all over three or four days, and it's 100% bled, hard lever. Not sure if it was more laziness or to prove a point, but it worked! Even if you bleed there are always a few small air bubbles "hanging around" this can be done cover on, occasionally after any brake work to achieve and maintain a hard brake lever.
What I find usually causing brake sticking is dried out brake fluid "crust" built up in the seal groove in the caliper. This forces the square o-ring seal out more and the piston sticks. It could also be any of the things mentioned above so the bottom line here is the system needs to come apart for a thorough cleaning.
On this riff. Technically gravity causes brake fluid to move down that displaces the air upward. Small line diameter, surface friction, brake fluid is "thicker" than water, gravity does it's job slowly, the brake fluid has to kind of ooze around the obstruction caused by the air bubble(s) in the line. Even when using vacuum and power bleeders; time is your friend. After any bleed job I set up the uphill path and WALK AWAY for at least 15 minutes, come back, slowly squeeze release lever, repeat this cycle a time or two.
CoconutPete
1979 XS650 Special
Taking the front brake system apart to do a good cleaning etc. is a wonderful sunday afternoon project. Even the novice wrencher can accomplish it and it results in that "open a beer and look at it for a while" feel good moment after.
hogtyed
Paul
Thanks for the replies. I have plenty to do this weekend. Tear apart brakes on the XS650 and clean and replace line. I get my Amals back for the Norton and then I’ll reassemble and install those. After that, I need to find out whats wrong with the Harley ignition. Lots of wrench turning for me. One of the joys of multiple bikes. On the plus side, both vehicles run like a top.
hogtyed
Paul
Fixed the caliper. It had some surface rust holding it from releasing. Still have a braided line in the near future. At least I got to ride her into work today. Needs steering head dampered.
