1977 GS750 Front Brake Rebuild - HELP!

[Guest]

Hi folks, I'm just finishing the restoration of my 1977 GS750.
The bike was a US import (I'm UK based) and when I bought a caliper rebuild kit I was surprised to find that the piston seal was far too large for my calipers, and there's a dust boot that I can't see a groove for it to sit in.
I know the rear dust boot sits over the caliper body, and I believe the front is meant to slot into a groove in the caliper, but I only have a groove for the piston seal.

1. Can anyone advise if there are two sizes of piston? Which might explain why my piston seals appear to be too large
2. Am I missing something with the dust boots? None were fitted to the calipers when I stripped them down but the bike has been a project for many years with many bodges so this isn't a surprise. I just can't see how they can fit into the caliper body without a groove for them to fit into.
3. I'm missing one of the little metal stopper plates that fits into the caliper mounting bracket to prevent the pads from spinning. Are these available anywhere? They're not listed on CMSNL as a separate part.

I'll go up to the workshop and measure my piston and the new seal tonight and will update with those dims. I'll grab some pics of the calipers too to help with the
Many thanks,
Tom.

 

[KiwiAlfa156]

If the seals are the wrong size its probable that the boot is the wrong part too. Could the caliper have been swapped out for a later unit? Some pics might help.

 

[Suzukian]

You need to go to a site like Partsila.com and look up the parts for the brake system. From the line drawing, you should be able to discern what's going on. You should look for a Factory Service manual. There are many in .pdf form online, manuals.lib has some. That will give you the definitive answer. Especially with a bike that people have bodged. Sent you a PM

 

[Big T]

The standard/wire wheel/ single disc front brake model has a larger diameter piston and seal.

It sounds as though you have an E model with dual front discs/ cast wheel? Although, that came out in 78

 

[Guest]

So, I've done some digging.
I have one twin disc caliper with a 38mm piston and one 43mm single disc caliper. Told you people had been bodging!

I need to buy another twin disc caliper basically. It wouldn't surprise me if the bike is a 78 model - nothing else on the bike was done properly so why would import docs be any different lol.

 

[allojohn]

What's the engine & frame numbers?

 

[Guest]

What's the engine & frame numbers?

I'll have to get back to you on that, I know the engine and frame numbers don't match which apparently is how it came from the factory (is this true? read it on a few forums now that they rarely matched).
The bike isn't at home, it lives at my in-laws so I'll have a look over the weekend.

 

[allojohn]

The '77-'79 models certainly did not match.

 

[Suzukian]

That '77 is one fine motorcycle!

 

[Guest]

Here's the single setup on my 77. What does your master cylinder look like?

I have that same bike, I put an 83 1100 engine in it..

 

[Guest]

I am looking for a master cylinder rebuild kit for a 77 GS750. Any ideas where to find one.
Thanks

 

[salty_monk]

You can use an 14mm bore MC that you can find..... Plenty of single brake stuff around with that size and a mirror mount if you're not completely hung up on originality.

Should be able to find something similar at https://www.mikesxs.net/ or https://www.z1enterprises.com/motorcycles/Suzuki/GS750 8-Valve/all-models/1978 or there are a few others people have used on here....

Some rebuild kits here: https://www.cruzinimage.net/category/item/itemgenre/motorcycle/suzuki/suzuki-brake/

KL stuff tends to be sh*te for master cyl.

 

[Suzukian]

You could convert that to dual discs for not much money. There are a lot of spoke rims, and dual discs on EBAY. I'm presently putting an GS1150 front end with a GS600 17" front wheel on my '83 GS750ES, as 16" tires are becoming scarce. The rims are virtually identical up to 1997. I have a spare set of TOKICO calipers with right hole spacing for the GS1150 front end (I just have to put a couple of washers on each side to center the calipers), all which will slide right into my '83 GS750ES neck. I've gone threw so many ads for so many wheels, but the calipers are going for around $ 45 bucks ea., matched up with the right Master Cylinder, and some fork legs, you will have a lot more stopping power. You will also know exactly what you have done to your bike, and that's a great feeling. My GS1150 conversion, including rim, new discs, complete front end, is running about $ 275 bucks.

I belong to the VintageSuzuki forum in the U.K.. Those guys are an incredible bunch. Don't go their if your thin skinned though, they will eat you up, they dish it out, but they can take it too. It's been a blast.

Not like the sideways cowardly attack I just received here. I have to bite my tongue here. I don't know if this site has moderators. I Administrate a forum of 52,000 people, I have 4 moderators and I would have banned that person for his attack on me, or any other member.

 

[salty_monk]

You probably also have have one fork leg from a single brake model and one from a dual brake model and different size brake disks too.. someone just added the extra leg from the later model rather than swapping both….