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GS750E Brake Rebuild

  • Thread starter Thread starter Drummert
  • Start date Start date
You're going to need patience taking the Piston out...I gouged the crap out of mine and just ordered new OEMs.
Actually, that went quite easy as soon as I put enough brake fluid in and just pushed them out like that. Yes, it screwed up the paint of the calipers, but they had a 40 year old paint job on them... I guess they were due for a new layer of protection anyway.

Ok, I promised some Belgium orientated pictures!

Brake Calipers masked up

UMs7j34.jpg


6RevAnB.jpg



Painting process

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Second day of painting, decided I wanted the squares on the back to be painted as well (fun note: I had to take the newspaper of first :P)

Ij9K6Ba.jpg



Taking apart the master cylinder, I found this when I pulled the lever. Ouch! Guess how all the muckus came in.

LLiZL2h.jpg



Jup. Muckus.

i4q2JaE.jpg



I'm working on the parts on the balcony, little heater up, since this is our situation right now.
BrUxWiK.jpg




And I had to buy myself some circlip pliers. Guess I will need those more often anyway. Let's hope next week those are in, then its cleaning and build up again.

I'm excited, since after that I will be able to finally tune the engine and then start driving again, after more than a year being bikeless... Battery is already hooked up to the trickle charger and got the parts to tune it lying around close as well.
 
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And here's the end result of the painting! Cured and all, my girlfriend didn't even mind me curing them in the oven ^^

Now unfortunately, I bought some circlip pliers online, but they got lost in transport... So I'm now for the time being stuck on pulling the master cylinder piston out...



cUzW7OB.jpg
 
The pliers came in, so today it was time to pull the piston out of the master cylinder and clean all the parts. Originally, I had the naive idea I would be able to put everything back together today... That didn't quite work out.

Cleaning everything was easy enough. But then the master cylinder... No circlip visible in the hole where the piston is. I start worrying, thinking the little holes you can grab it at rusted off (would be my kind of luck). I spent nearly an hour carefully scratching of dirt and rust to come to the conclusion that I definitely see no circlip, nor the holes to grab it.

0yV7Sb3.jpg


I decide to put the small screwdriver in sideways and wiggle around. Something comes loose!.... A white plastic ring... never saw that on a diagram.
I look again.... Again no circlip visible.

sOuIFxS.jpg


After scratching away at the dirt and rust I finally find something that looks like a circlip at first.... but its a metal wire. Also never seen on a diagram.

ksVrvit.jpg



I start to doubt myself at this point. Do I have the right diagram? Did I even order the right replacement parts. Who will know... Then finally, after scratching away for another hour, I find the circlip, completely clogged up in such a way that the holes to remove seemed to be part of the housing. I try and put the pliers in... pliers are to wide. Time for the dremel then... Spent at least 45 minutes grinding the pliers to a fit. Total time to pull the piston out: 2,5 hours...

Needless to say, I didn't put things together after that. Actually, the piston jumped out with a push from the bottom, leaving me to figure out how the parts where in there, luckily the parts left an imprint on the rubbers, so I should be able to figure that out relatively easy.

Me little cleaning setup in the living room, since weather outside is not my favorite:

Start

rLGBHqi.jpg


Two hours in (not counting the extra time for the master cylinder piston..)

BicrXgs.jpg
 
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I think I figured it out regarding that plastic ring and metal wire: I believe they should go on the outside of the rubber seal you put on top of the piston, so that the seal stays put. I wouldn't exactly know from taking the whole thing apart, the old seal was completely torn already. No way to see if they were originally on the outside, but I believe the exploded diagram in the manual shows it like this and it does make some sense.

I also don't fully rule out someone before me screwing this up and putting it back together completely wrong...
 
Pops up another question as well... Rebuilding the calipers now. How do you guys fit the dust cover around the outer lip where it stays against the caliper? I see how it grips the piston, but I can't seem to get the little lip of the seal around the tiny edge where it should catch...
 
Found my answer, to whom it might concern:

1. put the piston seal in
2. put the piston in, but not fully
3. put the dust seal on the piston and let it fall in the groove on the piston
4. let the piston slide in the piston barrel
5. the dust seal now kinda stays in place because of the piston, gently go around with your fingers.

Worked for me. Still a pain in the a**.
 
Brake calipers are together again. Started on rebuilding the master cylinder today. Obviously I ran into something: the circlip thats was put with the new piston cup set was too small.... First of all I thought I just couldn't get it in. Went to a shop in town thinking they might succeed since they do it way more often than I do. After 5 minutes of puzzling around, the guy goes: 'Dudes gave you too small a circlip man...'

Seemed to be the same size as the other one though, but I can push it down with my fingers, which I guess I shouldn't be able too. Also, the piston is able to push it out again, that's more problematic...

Can I bend the circlip, making it a little wider? Otherwise I guess I'll just have to go search the stores for a collection of circlips.
 
What kind of circlip pliers are you using - inside or outside? Some kinds of circlips will need to be pulled apart instead of squeezed together
 
Gotta say, this thread is going to be an awesome resource for when I rebuild all three of my brake calipers on my GS750. I do have to say: everyone keeps mentioning getting OEM parts for the brakes and I've poured through the forum with different searches looking for a good resource for OEM parts and have yet to find any. Is there a place where most folks here go to source the OEM brake parts? I'm especially having trouble finding stuff for my '78 GS750E. Any lead is appreciated, as I'm super wary of all the eBay kits.

Anyway, the calipers look great! I hope I can get mine as clean and as decent looking after some paint!
 
Is there a place where most folks here go to source the OEM brake parts? I'm especially having trouble finding stuff for my '78 GS750E.

If you're not worried about originality there is also the chance to upgrade at this point.... there's a link in my signature. works on this bike.
 
If you're not worried about originality there is also the chance to upgrade at this point.... there's a link in my signature. works on this bike.

Listen to this man, he knoweth of what he speaks.
Apart from that, the silly little round hockey-puck pads of the earlier bikes are verging on bloddy useless.
 
If you're not worried about originality there is also the chance to upgrade at this point.... there's a link in my signature. works on this bike.

Listen to this man, he knoweth of what he speaks.
Apart from that, the silly little round hockey-puck pads of the earlier bikes are verging on bloddy useless.

I'd definitely be interested in doing this, but it's a little pricey for now. I think I'll start with a rebuild to get the brakes workable and the bike more rideable, and then look to upgrade. I also don't have a ton of confidence in having to drill out mounting holes for a rotor. I don't have a drill press or anything to put together a good/precise jig right now, so a rebuild is the best way to get me safely on the road right now. Anyway, didn't mean to jack the thread!
 
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