Brake system losing pressure

[Nessism]

JC,
Sounds like the problem is the calipers. Something is causing the sliding caliper to retract too far away from the disc so an inordinate amount of piston travel is necessary before the caliper makes firm contact with the disc.

I think it would be appropriate to pull the calipers back apart and check everything out on the inside. Also, make sure the sliding pins are greased, the pad pins are greased, and everything moves freely.

 

[rustybronco]

JC,
Sounds like the problem is the calipers. Something is causing the sliding caliper to retract too far away from the disc so an inordinate amount of piston travel is necessary before the caliper makes firm contact with the disc.

I think it would be appropriate to pull the calipers back apart and check everything out on the inside. Also, make sure the sliding pins are greased, the pad pins are greased, and everything moves freely.

I 2nd the opinion. if I may add, are the pads wearing un-evenly? (looking for bent components here)

with a properly cleaned, polished (if necessary) bore, CLEANED piston seal groove, polished piston (if at all necessary) and lubricated with brake fluid, two thumbs pressing on the piston after it is initially started will easily push it back in the bore.

 

[J_C]

OK thank you folks. I will focus my attention there, including looking for bent components. Ed, would you be willing to sit in on this endeavor?

 

[KRISTI'SGS550]

OK, so if anyone know what you are going through it is me. With my CB650, I spent tons of time and money trying to get the front brakes to work. I replaced everything that could be replaced. This included a braided brake line, new banjos, rebuilt the caliper and the master cylinder. I did just as you did, continually pumped the brakes, had nothing. Put the zip tie on over night, nothing. I finally bought a new mightyvac to save my hands and fingers. Still nothing. When I hooked the mightyvac on suction I heard a little air leak on the M/C. As long as the mightyvac was hooked up and applying pressure everything worked. As soon as I took the vacuum off the air would somehow get into the system. Then I got a good idea, you'll like this. I took the bolts holding the banjo's off and used the white tape that is used for air tools. I am not sure how smart or safe this is, but it worked. I guess over time the threads on my M/C got loose and the white tape closed these small gaps. The brakes work perfectly and are holding air.

Cory

 

[TheCafeKid]

Are you talking about using teflon plumbers type tape? That stuff has a billion uses And I dont see anything NOT safe about it perse, as long as its not leaking, and not drawing air into the brake system.

 

[Nessism]

OK thank you folks. I will focus my attention there, including looking for bent components. Ed, would you be willing to sit in on this endeavor?

If you want the job done this weekend you are going to have to come to Torrance since my son is with me. Have plenty of garage space and tools. I say we strip down the calipers and have a look inside - or at least, check to see if everything is floating and sliding the way it should.

Let me know.

Ed
310-809-6038

 

[J_C]

I'm extremely pleased to report that the problem was identified and corrected. It took Nessism all of 30 seconds to identify that one caliper piston wasn't working AT ALL. The right disc was hot with use, the left was stone cold!

Yes, today I rode about 30 minutes south to meet nessism and get his expert feedback. Sure enough, all who mentioned the calipers were correct. I'm exhausted so I'm giving the short run of this story. Ed and I took the calipers off, disassembled them, checked out the internals, and put them back together. We also found I hadn't put the dust covers on correctly, so that was fixed as well.

I believe the calipers were stuck because I failed to grease the floating pins correctly (or at all) when I rebuilt them a year ago. However, the problem was fixed and I now have much much better pressure at the lever, and it stops much more easily as well.

Unfortunately the new brake pads that came were the wrong size, so I'll have to get an RMA for them. But the current ones have enough life to do the trick for some time to come.

This was my second time meeting a GSR member, and I was lucky enough to have done it within a week of meeting the first (chef1366). I can say that Ed is an awesome guy, and I appreciate how extremely generous of his time he was. This really is an incredible online community when I've been able to receive so much help from its members, and to meet two really great people.

Now that I've seen Nessism's BEAUTIFUL bikes, I feel like I should turn back to some more cosmetic issues I have Thank you Ed; I do feel much more safe on the bike and ready for the SoCal ride and Yosemite!

 

[Nessism]

Glad to hear the brakes are working better Jeff.

I'm pretty sure the caliper pins binding are what was causing the problem. The rubber dust covers being out of place shouldn't cause the problems you were having.

Since the master cylinder you are using has that small 14mm piston, the brakes will never have a super firm feel. As we talked about, changing to a dual disc master will firm up the lever further, and installing stainless/teflon lines would also help. These things are optional of course as long as the performance is acceptable to you as is.

Enjoy and glad to help.

Ed

 

[Guest]

COOL! Glad you got that one sorted! Put on your old M/C. Shoot, it's got a fresh rebuild on it and it's made for the bike.
Thanks Ed for keeping Jeff safe. I didn't feel safe with those brakes and I was hitting the throttle rather hard. Checking my carb work.

 

[salty_monk]

I have one off the skunk but that likely needs a rebuild too....

Dan

 

[J_C]

Well it actually feels pretty darn good now.... I don't have any complaints in terms of pressure. I can still bring the lever all the way in, but it takes all the strength I have to do it. There might still be a tad bit of air, but I've had it on it's side stand for a few days so I'll tap the lines a few more times and call it quits. Plus, the MC I have (from a 750 or 850 originally??) has a tad bit of corrosion in it, so I'm going to pass on that for now.

Thanks guys! =]