Front brake master cylinder wont pump fluid

[Bustedknuckles]

Picked up a 198? GS850 a couple weeks ago for $200 bucks. Seems to be in decent shape but needed some work and has been sitting for a little while. I wanted to get some input on a specific problem that I was having and I'm not sure the best way to proceed.

First off, both the rear and front brakes seem to work fine rolling it around in the garage. But the front brake master cylinder was basically filled with a shallow amount of semi dried goo.. It still applied the brakes when the lever was pulled but after taking it off and spraying it off/out as best I could, filled it back up with new brake fluid, the lever can be pulled nice and easy and the action is nice and smooth. But there is minimal resistance to the lever and it isnt pumping fluid or applying the brakes. I took all of the hoses apart and off of the calipers in addition to removing the bleeder screw, but minimal dirty fluid came out. But it was still liquid and not dried or gooey.

I want to go the most "financially-friendly" route I can while still being safe. What would you recommend the next steps be in trying to salvage what I already have? Thanks in advance! ~Nate

 

[Runeight]

I would suggest rebuilding the entire MC along with a professional cleaning. I always rebuild a MC in my builds. It's not difficult but my local garage does the cleaning. No substitute or short cuts for braking.

 

[loud et]

Sounds like you need to bench blend the master cylinder.
You tube it. It's easier than me trying to describe it.
Then a proper front brake bleeding.

If you have goo in the master cylinder then you should also remove both calipers and fully disassemble them and clean them also.

 

[chuck hahn]

Get a mighty vac if you intend on bleeding brakes often..such as if you have several bikes or plan on building more. Harbor freight has them for around 25 bucks and they save all the bullschitz. wrapping some thread sealing tape around the bleeder threads helps dramatically as well so your not sucking air around the threads and wasting your time and energy. Mighty vacs eliminate trying to prebleed the master cylinders. Hook all the lines up and tighten the banjo bolts and be done in 5 minutes.

http://www.harborfreight.com/brake-bleeder-and-vacuum-pump-kit-69328.html

 

[Bustedknuckles]

So rebuild the MC, completely disassemble and thoroughly clean the hoses and calipers, reassemble and give em' a good bleedin? I don't think its a matter of it needing bench bled since i got everything back together, filled it with fluid and tried to start bleeding it. The problem is that it wont pump any fluid. The lever has little resistance and I cant get any brake fluid to come out of it. So the MC's bad?

 

[loud et]

So rebuild the MC, completely disassemble and thoroughly clean the hoses and calipers, reassemble and give em' a good bleedin? I don't think its a matter of it needing bench bled since i got everything back together, filled it with fluid and tried to start bleeding it. The problem is that it wont pump any fluid. The lever has little resistance and I cant get any brake fluid to come out of it. So the MC's bad?

Bench bleeding gets the fluid into the bore so it has thrust and gives a full pump of fluid when you squeeze the handle.
Trust me, bench bleed it and you will see how firm the handle gets. It will have full resistance and push fluid through the bleeders.
If that doesn't work then you have frozen caliper pistons or plugged brake lines.
If there was goo in the system , anything is possible.
Only by removing the whole system and cleaning it will you know the true extent of your brake system needs and deficiencies.

 

[bobgroger]

Also there is a very small return hole near the outlet that needs to be clear. These plug up then your brakes lock up and start smoking, or possibly toss you over the handlebars. Any old GS most likely needs both master cylinders and all 3 calipers cleaned with new seals, and new brake hoses. Suzuki recommends hose replacement every 2-4 years, how long do you think it's been?

 

[Bustedknuckles]

Bench bleeding gets the fluid into the bore so it has thrust and gives a full pump of fluid when you squeeze the handle.
Trust me, bench bleed it and you will see how firm the handle gets. It will have full resistance and push fluid through the bleeders.
If that doesn't work then you have frozen caliper pistons or plugged brake lines.
If there was goo in the system , anything is possible.
Only by removing the whole system and cleaning it will you know the true extent of your brake system needs and deficiencies.

yeah, what gets me is that the brakes were working fine before I took it apart and there was liquid brake fluid in the lines. Granted the reservoir was not exactly in the greatest shape... All I did was take the MC off the bike and spray it down really well. Put it back on, filled it up, but no matter how many times I pump that lever, the fluid level remains the same and I am getting no firmness in the lever, no bubbles, no fluid movement, nothing.. The only youtube videos I can find are showing that I am doing it the right way. Which leaves me thinking that its likely a bad MC?

 

[Nessism]

We are talking about brakes here. Do the job right, your life may depend on it.

Fully tear down the master and calipers and clean out the sludge. Make sure the small return port on the master is not blocked. Throw the brake lines in the trash because they are now lined with scale and you can not clean that crap out. Personally, I'd replace the caliper seals but you can try to reuse them if money is tight and they are not leaking.

After everything is back together you need to prime the master to make it pump. Drawing a vacuum on the caliper bleed nipple is the easiest way. Once the master cylinder bore is primed and filled with fluid the system will start pumping.

 

[Bustedknuckles]

I ordered a new set of hand controls, MC and clutch assemblies. And I'll start disassembling the calipers tomorrow. Anyone know where I can get some affordable brake lines? Anyone on here have a good set?

 

[Nessism]

If you are handy with tools it's easy and cheap to make your own lines from Earl's parts. Check this thread for more info.

If you want premade lines there are various companies, including this one...http://www.rennsportautoparts.com/Default.asp

 

[bobgroger]

If you are handy with tools it's easy and cheap to make your own lines from Earl's parts. Check this thread for more info.

If you want premade lines there are various companies, including this one...http://www.rennsportautoparts.com/Default.asp

+1 for Rennsport. Coastguard1975 on ebay. Good stuff, reasonable prices.