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Front MC - Order of Assembly

  • Thread starter Thread starter rickt
  • Start date Start date
R

rickt

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I'm ready to reassemble the front MC on my '78 GS750. The attached photo shows the parts removed from the original MC when I disassembled it. Several of these parts (E=plastic washer, G=metal spring clip) were not in the Suzuki rebuild kit. Are these pieces critical for proper function of the MC? Is this the correct order of parts for assembling the MC?

Help would be appreciated.

rickt
 
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Well, I've never rebuilt a master cylinder, I've only replaced them...but as for your question, that is one part of the bike that I would never skimp or guess whether it's right or not. If the part was in the cylinder to begin with, make sure it's in there after a rebuild. If it wasn't in the kit, I'd hit up your local shop and see if they either have the part or ask if it is a servicable one or if it must be replaced in the build. cha-ching=2 cents.
 
my 78 550's master cylinder looks to be pretty much the same as yours except for the parts you've mentioned. Part G seems pretty much superfluous, as does E. All the action happens with the rubber bits anyway. Have you tried putting it back together to see if it works at all without them? Beyond that, check the exploded view at bikebandit or something and see what they look like. 2 more cents.
 
brand new bike zealot said:
my 78 550's master cylinder looks to be pretty much the same as yours except for the parts you've mentioned. Part G seems pretty much superfluous, as does E. All the action happens with the rubber bits anyway. Have you tried putting it back together to see if it works at all without them? Beyond that, check the exploded view at bikebandit or something and see what they look like. 2 more cents.
Click to expand...

lol! :rolleyes:
 
When I rebuilt mine I only used the spring, rubber nipple, copper penny type du-bob, piston, e-clip and dust cover. In that order.
I did not use a circlip or any of the extra washers you have pictured.
Bike bandits pic is very vague.
 
I'd reuse the old plastic washer. G looks like a spring clip to hold the outer boot on. Did you get a new boot? At any rate, reuse the old one if there is any reason to.
 
Parts in the Kit

Parts in the Kit

Here's a pic of the parts found in my MC rebuild kit. No white plastic washer and no wire spring clip, but a new boot. There was a boot on the piston when I disassembled, but it got destroyed in the process. Guess that's par for the course with a bike that sat for 25+ years. The thought did enter my mind that the spring clip was designed to hold the boot in place.

Anyone have insight on this possiblility? How would one go about putting it back into place?

rickt
 
A and B are backwards. The flat side of the rubber cup (A) goes against the left side of the main piston (C). Then the small end of B goes into the cup side of A. If you look at the flat side of the old rubber cup(A) you should be able to see marks from the metal strips on the flat end of the piston(C).

I know my 750 had that plastic washer (E) and I reused it, but I'm not absolutely sure where it went. I think the order is metal washer(D), circlip(F), plastic washer(E), then the boot with the small wire clip(G).

I seem to remember that getting the circlip out was a real pain in the butt because that plastic washer was on top of it and in the way and it was all so full of muck I couldn't tell what was going on in there.

Sorry I can't be more help, but it's been a few years since I rebuilt mine.
 
rickt said:
Here's a pic of the parts found in my MC rebuild kit.

rickt
Click to expand...

Where did you buy your rebuild kit and at what cost?

As far as the boot goes, it just pops into a groove in the m/c body and another on the piston. It's fun getting it in there without tearing it. A clip shouldn't be necessary...
 
I've purchased all of my restoration parts for this bike from Flat-Out. There prices are the best I have seen. The MC kit (part # 59600-45821) was $28.99 online.

rickt
 
Really confused!

Really confused!

Well, I thought I knew the order of assembly for the front MC, but it appears that I was mistaken. Here is another photo of the new parts from the rebuild kit.

A= old master cylinder (not new)
B= rubber cup with nipple on open end that would seem to go into the hole in the top of spring C
C=spring - narrow end with small hole - wide end with large hole
D=metal dish that would seem to go into the wide end of spring C
E=piston that would seem to go into the MC as shown in the photo (i.e. narrow end first
F=metal washer
G=circlip
H=rubber boot

So, am I correct with assembly of B-C-D?
If so, which direction does this go into MC A?

We're expecting a foot of snow in the next two days and I may have the opportunity to put this beast back together instead of going to work.

Help please!

rickt
 
E, F, G, and H are in the correct order and E is facing the correct direction relative to the master cylinder.

However, you need to swap B and D in the order: (this assumes B is the all rubber part, and D is a metal assembly)

The flat side of B goes against the end of E that is facing the master cylinder.
The small end of C goes into the concave cup side of B.
The round side of D goes into the large end of C.

So, they go into the cylinder of the housing in this order:

D, C (wide end first), B, E, F, G, H
 
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Paul,
Thanks for the detailed description. I think that even being as mechanically challenged as I am, I'll be able to get it together in the right order. I really appreciate the information.

Next on the agenda is the rear caliper and MC.

rickt
 
Front MC Final Phase

Front MC Final Phase

Almost ready to take the final plunge and reassemble the front MC for my '78 GS750.

Just a couple of final questions. The attached photo shows the pieces from the rebuild kit and the two pieces that came out of the original MC, but were not included in the kit (plastic washer D and spring clip F).

So, based on the info from Paul, assembly A goes into the barrel followed by piston B and then washer C. In my stock MC plastic washer C went in next followed by circlip E. The spring clip sat in the same groove as circlip E, but I don't know its purpose.

To my primary question - Does the rubber boot G slip over piston B until the inner lip of the boot (tried to show with a line) rests in the groove in the piston B (shown with dark line)?

Has anyone encountered a spring clip such as F? Any ideas on its purpose in life?

Thanks,
rickt
 
I think E is a nylon spacer that you will re-use because they dont wear out, G is in my opinion the remnants of the boot that isn't pictured. It held the boot in place to keep crap out but has in 30 years just rotted away and left the ring. The new boot if found probably has the ring included.
 
rickt said:
To my primary question - Does the rubber boot G slip over piston B until the inner lip of the boot (tried to show with a line) rests in the groove in the piston B (shown with dark line)?

Has anyone encountered a spring clip such as F? Any ideas on its purpose in life?
Click to expand...

I wish I could help, but I don't remember exactly how the boot went in. It's been a few years since I did it. I don't recall it being particularly difficult, or I probably would remember! It does go on after all the rest of the parts are in place including the circlip that holds the piston in against the pressure of the spring. At that point I think you just slide the boot in over the end of the piston with the wire around the outside of the boot at the base. I does make sense that if there's a rib on the inside of the boot that is the right size to fit in the groove on the end of the piston that it would go there, but I wouldn't force it. Once you get everything in and the circlip on, it might be obvious how the boot fits and where the other wire ring goes. Once it's all together the boot can't go anywhere since the lever is against the end of the piston, so as long as it prevents dirt from getting in I don't think it's that critical.

Good luck.
 
Well, I finally pulled out the manuals (factory, Chilton, Clymer and Haynes)and it looks like they all show the order as piston, steel washer, circlip, boot, plastic washer, then the wire ring...
 
Paul,
This diagram seems to fit with what I remember from taking the MC apart many months ago. I pulled the rubber boot out with needle-nose pliers and I can imagine that the nylon washer and the wire clip probably remained in the barrel of the MC. I just assumed that they were installed first followed by the rubber boot. You know what they say about assumptions! It makes more sense that the nylon washer and wire clip were designed to hold the boot in place.

So, I will put things together in this order and see what happens. I don't imagine that much bad can happen as long as the piston, spring, etc. are in the right order.

Just out of curiousity, where did this diagram come from? If from a factory service manual, do you know where I can find one?

Thanks again for the input.

rickt
 
The same diagram is in all of the manuals I mentioned. Clymer, Haynes, etc. often reuse pictures and diagrams from the factory manual.

I have a spare factory manual for the early GS750. I'll send you an e-mail with details.
 
Just to complete the story, I reassembled the MC last night. Once the metal washer and circlip were in place, it was clear that there really wasn't anyplace for the nylon washer (D) and the wire clip (F) to go. After the boot was worked into the barrel and over the slot in the piston, everything looked correct. I could not see any real value in pushing these two pieces (D & F) over the rubber boot. The boot appears to stay seated when the piston is compressed and released.

Hope this story might help someone else struggling with a MC rebuild. Now for the rear MC and caliper!!!

rickt
 
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