Caliper piston wont go back in.

[Nessism]

That is absolutely the WORST POSSIBLE thing to do!!!! (Note my sig-line about free advice)
Never, ever back-flush the minerals/moisture that has settled to the lowest points in the brake system INTO the master cylinder!!!!!!! Sure fire way to ruin a working system!
Use a line-lock to stop the flow to the master while opening the bleeders (that you have already drilled the rust out of so that they flow like new) and then retract the pistons back into there bores while the dirty/garbage old fluid
is expelled form the system.

If the calipers are full of "dirty/garbage old fluid", then why are you suggesting anything other than a full system tear down? As far as a "line-lock" is concern, why in the heck would you suggest such a thing? Go spend $70+ bucks on a device so "dirty/garbage old fluid" isn't sent back into the system? Umm, bad advice there. If the fluid is old and chunky the system needs a full tear down. I suggest a full tear down on ALL old GS brake system. Change the lines while the system is apart. Workarounds like using a "line-lock" is a great example of the bad advice you expound about.

[chuck hahn]

And...one can suck all they want out the bleeder but it will NOT remove the sediment thats sitting in the bottoms of the wells....which is gonna instantly contaminate any new fluids added. Bet when he opens them up he finds that brown slime gunk all over the place..even on the back of the piston itself.

[Nessism]

[chuck hahn]

Yup.....that will all clear right up with a little bleeding.....NOT!!!!!!!!!!!!

[tkent02]

No brown sugar in that photo? I like it when the brake fluid turns to brown sugar.

[slyone]

Kinda glad I found this thread cause I took apart my front brakes on my 79 850 today & did find some crap & the slider boots are really broken down. The lines look good even though they are original? This little crap is expensive too! Like $300.00 for rubber & pads

[GateKeeper]

If you value your life, then do a full and complete tear down and rebuild of your brake system, front and rear, if your not the original owner and know for a fact 1000 percent if and when it was done, DO IT ON YOUR OWN......

30 year old lines need to be replaced, period, they were actually supposed to be replaced every 3 to 5 years......but no one ever did

If the pistons are good, no need to change them, replace the rubber bits and your good to go, replace the pads even better, and if you change to Stainless Steel brake lines you now have almost the best you can get.....

I just did an 85 Yamaha, I didn't even have to think if I was gonig to teardown the brake system, it was just done, as it was for my 83 GS and I had the bike for 20 years.....

Brake overhaul is cheap compared to a malfunction and you and your bike end up damaged.......or worse......

.

[Nessism]

Kinda glad I found this thread cause I took apart my front brakes on my 79 850 today & did find some crap & the slider boots are really broken down. The lines look good even though they are original? This little crap is expensive too! Like $300.00 for rubber & pads

These prices don't sound right. You might want to do some research. You can save a bunch of money.

[slyone]

These prices don't sound right. You might want to do some research. You can save a bunch of money.

I know..right! Thats from GSSuzuki dot com at their discount off retail. Thats front brake all rubber components and pads...thats it My pads seem thick but somewhat contaminated I believe- not sure they'd sand out? I believe the one piston seal may be leaking....

[Nessism]

I know..right! Thats from GSSuzuki dot com at their discount off retail. Thats front brake all rubber components and pads...thats it My pads seem thick but somewhat contaminated I believe- not sure they'd sand out? I believe the one piston seal may be leaking....

You can get pads for cheap from ebay. As for the leaking, you need to pull the piston out and inspect it before deciding what parts you need. Brake lines are about $100/set. Earl's parts or order from ebay for those too if you'd rather.