81 XS650 special: caliper, hoses, or master cylinder????

rsylvstr · Full Member Joined: Aug 09, 2008 Posts: 65

Last year the front brakes would seize up, I'd bleed them they'd work, then seize again. i then decided to take apart the calipers and pads and clean them thoroughly. i then reinstalled and flushed the master cylinder, lines and caliper using a mityvac and then did the old squeeze and bleed routine. she would still seize once in a while and if i cracked the bleeder valve, pump a few times she would be fine. got her out of the shed today and she was seized so i bled her and she's fine. however i can't keep doing this all year. which parts do i start replacing?

oldbikenut

I just ordered from Mikes xs all new parts for my front disc which included the rebuild kits for the master cylinder and caliper. I also ordered both new hoses and brake pads. I spent just over $100.00 but I think it's worth as I want to be able to stop!

yamaman

Can you tell us what you mean by seize? Are they locking on, or not coming on when you apply the brake?
Seize to me means stuck, wont move any which way! Rusted or welded solid!
1 air bubble in the system will stuff the lot, are you positive there's no air in there?

oldbikenut

oldbikenut wrote:

I just ordered from Mikes xs all new parts for my front disc which included the rebuild kits for the master cylinder and caliper. I also ordered both new hoses and brake pads. I spent just over $100.00 but I think it's worth as I want to be able to stop!

Now I should say my rear brakes were good(don't know why)but I did take everything apart cleaned and flushed the system and it's good to go!

rsylvstr · Full Member Joined: Aug 09, 2008 Posts: 65

they are locked to the caliper. i actually wondered if a new bleeder valve would help...in case i'm sucking air.

xjwmx

If there was air in it and the caliper pistons were seized, the lever would squeeze in, but it wouldn't do anything, bevause the air would just be compressing (liquids won't compress). If there was no air in it and the caliper pistons were seized, the lever wouldn't squeeze in.

jayel

in the bottom of the master cylinder reservoir cup there are two holes that need to be open for the brake to work properly one is about 3/32 you can see it, the other is hidden under a tab, it is very small .015 or so if you turn the fluid cup to the side you can get to it, if it is plugged the brake will lock on (seize), the inside of your master cylinder is probably full of crud, that is why it will sieze sometimes and once you bleed the brake it works again for a while until that small hole plugs again, this is very dangerous, what if it locks up on the highway? or in a corner? take that master cylinder apart and clean it properly, or take it to someone who knows what they are doing (Dealer?) and have it fixed right

rsylvstr · Full Member Joined: Aug 09, 2008 Posts: 65

thanks for the input guys. when i first squeezed the lever today, the piston (?) that it pushes in on the master cylinder didn't budge at all, no matter how hard i squuezed. once i cracked the bleeder valve, the piston on the master cylinder went in (as i squuezed the lever) and then i closed the valve and she worked fine.
last year, she froze up in a corner...and then in a straight line with me and my wife. i bled it at that point in a parking lot (disc was smokin') and we went on our way for another 90 mile roundtrip and worked fine.
sounds like i just need to take the master cylinder off and clean the heck out of it.

jayel

this is why you should change your brake fluid every year, that crud builds up over time, getting the plunger assembly out isn't easy with that internal C-clip but that's what needs cleaned out, make sure that little hole is clear it's what releases the pressure on the brake disc (allows the fluid back into the resevoir cup)

yamaman

Listen mate, you don't know enough about brakes!
Your prepared to put not only your life, but your wifes (you got kids?) on the line to save a few bucks, ridiculous!
Sorry to come out preaching, but really, what are you doing?
Wake up to yourself!

Be as offended as you like by my comments, but think about it at least!

oldbikenut

I think yamaman is correct as brakes are something that you want to make sure are working properly! I think we all need to know are limitations, I comfortable doing brakes but I have limited knowledge about the electrical aspects of motorcycles. We all need help at times and this probably is a good time for you to find someone to look at your brakes.

gordo

sylvstr, brake's are a safety item, DO NOT be cheap on your life,or someone else's!Take the master cylinder & the caliper totally apart & replace ALL the component's.As Jayel said, be sure everything is clean & open when you reassemble the component's. If there is any pitting on the caliper piston, replace it.On a bike this old( I have an '80 g model, and the same problem, I did what I'm suggesting to you),the hose's should get done, too.I went with the stainless,less money & a much better product. My lever is rock solid when applied,will lock up the brake if I squeeze hard enough. The front wheel spin's easily when I release the brake. You don't need to be a rocket scientist to perfotm this job. Only use brake fluid as a lube on reassembly,regular grease or oil will ruin the rubber seal's you just replaced.Brake fluid is not a regular oil type fluid.Special formula to prevent boiling at high temp's.And only fresh fluid from a sealed container. Brake fluid is hydro scopic, meaning it will absorb water,(IE humidity). So that is why you use only new fliud. Smile

The rebuild kit's from Mike's are good quality. Also, check to see if the bottom hole on the bleeder is open & round,mine wasn't,the PO tightened it way too much,collapsing the hole & it leaked.Found one at NAPA for$1.00.Got a manual? Good luck, Gordo

rsylvstr · Full Member Joined: Aug 09, 2008 Posts: 65

i got this bike last year from her father that passed away when i was in Iraq and in all honesty, there hasn't been much PM performed. my plan is to just get a rebuilt master cylinder and opcheck it.

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