Xs-1 front caliper locked up

[oldbiker648]

I have dis-assembled front caliper on '79 three times thus far, re-assembled and bled brakes, but the caliper still sticks. Master cylinder has been cleaned out twice, but not totally dis-assembled. Is it time to rebuild master cylinder? Also, should this bike kick start with a dead battery?

[btchalice]

sounds like you have bad hoses. when they get old the rubber inside can flap shut and hold pressure on the caliper. does it release if you open the bleeder screw?

[oldbiker648]

Do you mean releasing the bleeder screw when the brakes are locked up without touching the brake lever?

[andreashweiss]

I had this very same problem just recently front caliper sometimes both sides would stay on. I incorrectly assumed it was the calipers/pistons etc. I cleaned and cleaned rebuilt them etc . Was gettin very frustrated. I changed the master cylinder and problem disappeared. Get a NEW master cylinder. or find one fromt Yamaha seca with dual discs even the electrical connection fits and the seca had a nice metal master case. Not sure of yr to look for.

[oldbiker648]

I'm thinking you are right. One other option I'm looking at is gettin a 13mm Master Cylinder from Mike's XS in Florida. It's about $70 and I spoke with a guy at a Vintage Jap Bike met last year that had one and said it was way better than the original MC. I hope I don't have to replace the hoses as well, this is starting to run into some money.

[TopCatGr58]

Hey Oldbiker,

It's recommended that you get the 16mm MC, has better capacity for driving BOTH front calipers...the 13 is for a single caliper system!

The bike won't start with a dead battery using the kickstarter, the TCI needs ~10volts to run, so you need to either charge it up, or Jump from a NON running(engine turned off) car/truck or spare battery!!

T.C.

[buggrin]

MC & Caliper rebuild

My brakes performance had slowly deteriorated over the years until I finally realized they weren't safe. Sticky, rubbing, stuck pistons, poor lever feel etc. Finally bit the bullet and bought new pistons, mc & caliper rebuild kits, and SS brake lines. You're right, it ran into some money, but with lots of help from the forumites the job was fairly straight forward. Now the thing stops as good as it goes. Crappy brakes need more than bandaids.

[oldbiker648]

Thanks TC & buggrin,
The bike in question is an XS 650 Special II with a single disc, so the 13 MM MC should be the ticket. I've seen dual disc set-ups on some of the late model 650's, but not this one. I'll probably have to bite the bullet, as buggrin did, and replace the entire set-up. At my age, reliable stopping is at least as important as acceleration. I appreciate the advice of everyone that responded and will be placing a parts order this week.

[pggg]

Sometimes brakes stick because the 'sliders' are corroded or gunked and too stiff, they're the metal/rubber bushes that the caliper units 'float' on. Clean up and stick some oil in there and they slide smoothly.

[oldbiker648]

Yesterday I found the MC re-build kit and new piston I bought from Mike's XS last year. I'm going to pull off the caliper, replace the piston, grease up the spots you suggested, rebuild the master cylinder and see if that will solve the problem. If not, I'm springing for a new MC and probably hoses. I still have swing arm bushing and steering head bearing issues with this bike, but brakes are more important. Thanks.

[Lamric]

Oldbiker, this could be a blocked 'spooge hole' in the master cylinder not releasing the pressure, check out this tech tip

[DiverRay]

John
One last thing. DO NOT use just any grease or oil on the slider parts. I use synthetic grease only on all parts. It has a high (475F) melting point and can stand up to the heat with disks. some of the other grease or oils can melt and run into the pads, and ruin your breaks. Just smear a VERY thin film on the parts, after cleaning, and assemble.
Ray

[oldbiker648]

Thanks for the tip DiverRay, last thing I want is lubricant on the brake pads. Do you have a specific product recommendation or will any hi-temp synthetic work?

[Ken Talbot]

The auto supply shops like Napa carry silicone disc brake lubricant in a squeeze tube.

[oldbiker648]

10-4 Ken, I actually have a NAPA within walking distance from work, so they have been getting a fair amount of business as I get back into my 2 project bikes. My long-term goal after retirement is to really get to know my XS's inside and out and find out just what these old bikes are capable of. I already sense a good fit after a couple of years of ownership, and expect that to get better as my experience increases. I sure appreciate the help from you other XSives and gurus and aspire to gain your level of knowledge.