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Rear Brake Master Cylinder

  • Thread starter Thread starter Elielrosario
  • Start date Start date
E

Elielrosario

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Hey guys, I'm having a little trouble installing the piston set ('77 GS750). I've looked at the exploded views (and search here) but can't figure out the if the piece with the brass nipple goes nipple-up or nipple-down. Also not sure if the spring goes with the thinner end going up or down?


pistoncup-set_big6960045820-01_46d6.jpg
 
Assembly pic

Assembly pic

Elielrosario said:
Hey guys, I'm having a little trouble installing the piston set ('77 GS750). I've looked at the exploded views (and search here) but can't figure out the if the piece with the brass nipple goes nipple-up or nipple-down. Also not sure if the spring goes with the thinner end going up or down?
Click to expand...

This master cyl looks similar, check this assembly pic from Nessim on post #2 of this thread --> Rear Master Cyl Assembly Pic
 
Awesome! That helps a lot, I'll try it out today! (Praying brakes wont stick/drag anymore)

Thanks a bunch.
 
I just rebuilt mine last night so it's fresh in my mind.

The little brass tit goes into the end of the spring, and will be pointing up when installed on the bike.
So from the top, you have the first seal (lower right in the picture) spring, then the piece with the brass tit, then the shaft.
The concaved end to the bottom which mates with the domed end of the actuation rod.

http://www.boulevardsuzuki.com/fich...y=Motorcycles&make=SUZUKI&year=1980&fveh=2150

Hope this helps.
 
also make sure the tiny return hole in the M/C is clear. it is very tiny and located where the reservoir inlet is on the M/C. if this is blocked it will cause the brakes to stick on or not release properly
 
Wait... I feel like I'm getting two different instructions here:
1) the image that BTBARB shared, showing the order; and
2)Kiwi Canuck's assembly, which seems to be inverted (when compared to the images provided by Nessim btbarb's link)

Or am I just reading it wrong (it's been a long day)?
 
They look the same to me. let me walk you through the Boulevard Suzuki assembly:
At the top is the piece that BTBARB shows attached to the right side of the spring.
Just below the spring is part #2, which BS shows attached to the spring but BT shows just to the left of the spring but unattached and in two pieces.
First is the rubber seal, then a plunger. BS shows it as all one piece.
 
Gotcha. The boulevard Suzuki assembly link doesn't on my side. But I'm pretty i understand (again, long day).

I have a job interview after my day job (today), so hopefully I'll make it home in time to change it out and test ride.

Thanks again
 
Tried it but no fluid is going thru at all. Is the brass nipple supposed to have freeplay?
 
Hold that thought!

Hold that thought!

I may have steered you wrong, I checked the other pictures and it's different than I described.
I'll go and check again and make sure, and post a picture.
 
Kiwi Canuck said:
I may have steered you wrong, I checked the other pictures and it's different than I described.
I'll go and check again and make sure, and post a picture.
Click to expand...

Ignore my earlier post I did give you the wrong info, the picture link posted by btbarb is correct, my apologies:o
 
Thanks. The only other way I haven't tried it is using the same setup except with the nipple up. I had it that way before but with the spring's narrow/flat end facing up, I haven't tried it facing down and nipple piece facing up.
 
This it

This it

IMG_1149.jpg


This is the correct order, you must have a blockage somewhere else if you have tried this and it doesn't work.
 
Last edited:
New parts should be arriving next week, so I guess I'll have to wait until then to see if these are just damaged.
Thanks, I'll update in case someone later has a similar issue.
 
Yep, just done mine and exactly as per the picture. Leave the hose off or loose until the M/C has filled up or it will take a while to fill.
 
So, I found that the M/C needs to be primed a certain way in order for fluid to pump thru. It seems that I needed to put it together, fill the reservoir with fluid, and then from the top [opposite of the pushrod] pour some fluid, then push down the piece atop the spring to allow fluid to enter the chamber. I did that until it seemed to be completely full. Then the fluid flowed freely.

All parts (all oem caliper piston set, seals and rubbers, m/c rebuild set) came in the mail and were installed this week. I'll be test riding today if it doesn't rain much.

Also, this model m/c doesn't have that tiny return hole everyone talks about.
 
...worst luck ever: brake still locked up right after the first hard braking. Tomorrow I'm going to feed something thru the brake line to make sure nothing is clogged in there; and replacing the brake fluid with another "type" (I bought this DOT3 high temp stuff but idk if its really any good, I seem to be having more problems since I started using it).

I honestly don't know what else to do here, any suggestions would b awesome.
 
Sounds like you may need to replace the brake line, if it is a 30 year old rubber line, it wouldn't be the first one to start to deteriorate from the inside and cause a blockage.
 
It's a stainless braided line, that was the first thing I replaced about a year and a half ago
 
Did you clean out the return port of the master cylinder when you rebuilt it? If not, that's going to cause your lockup. It's a hole so small you can barely see it but must be cleared out so the fluid returns to the reservoir. You'll want to use a wire strand, about 16 or 18 gauge wire will do you, and push through the hole. If it doesn't, soak the master cylinder in some brake cleaner for a bit and try again. If not, look real close as I had one MC that I needed to have that hole redrilled - it just wasn't there like it should have been. For that, I found a machine shop in town as that hole is smaller than a drill bit you'll find at any store.

I just went back and read another one of your posts where you said it didn't have one. Trust me, it does have one and/or needs it - otherwise, those brakes will continue to lock up on you. Post up a picture of the MC itself please so we can look at it.
 
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