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GS850 Front Master Cylinder

  • Thread starter Thread starter Guest
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Guest

Guest
Hi all,

New here with a UK 1979 GS850, the the round top front master cylinder.

I'm currently trying to rebuild the front master cylinder as it started leaking, however I'm struggling to find parts for it. I have tried CMSNL but they don't list a part number. I'm wondering if there's any commonality with any of the other early GD models which do have part numbers listed?

Does anyone know the part number (or where I can find it) for the piston and seal kits for the early round master cylinder on the 850? All the kits on eBay etc seem to be generic kits for the later square style master cylinder.

I have also tried ordering 59600-45811 for the GS850GL but this seems to be about 5mm longer than the original part and to have a slightly different shape to the piston. It is listed as a superseded part so perhaps this was an intentional change by Suzuki?

I'd appreciate any advice/knowledge people have!
 
59600-45811 is the part that shows on the parts fishe. Did you try it? Before you do be sure to look at the master bore for any signs of aluminum pitting.

Just about any 5/8" or 16mm bore master will work. It's often easier to source something else, especially if the bore is corroded.
 
Thanks for confirming the part number. No I haven't tried it yet, I didn't want to open it up until I was sure it was the right part in case I needed to return it. My concern now is the piston is 4mm longer than what is currently in the master so I'm wondering whether this may cause issues with reduced travel and not being able to create enough pressure at the master end of the system to give good braking? Although as I said perhaps this was an intentional change...

And thanks for the advice on the pitting. My master seems okay fortunately and I would like to keep it to original parts if I can. If not I will just grab a generic 5/8" like you suggest.
 
My bike is 1980, at least most of it is. There is a round '79 m/c fitted.
Bike looks to have been down heavily at least once on the right side.
If in any doubt I would do as Ed suggests and get a replacement assembly.
You are back on the road sooner and you can put the old part on the shelf to get better or who knows what you might come across at a jumble sale :)
 
Why not use an EX650 master cylinder. Cheaper than buying parts & easier to get hold of. Slightly more modern look I guess is the only downside. If you choose the slightly older of the two easily available you also get a mirror mount.
You also get an adjustable lever.
 
shields17 said:
Hi all,

New here with a UK 1979 GS850, the the round top front master cylinder.

I'm currently trying to rebuild the front master cylinder as it started leaking, however I'm struggling to find parts for it.
Click to expand...

This may be a stupid question, but have you tried your local Suzuki dealer? I won't buy any aftermarket parts for the brake system, it is too crucial to trust jobber parts with.


Mark
 
Thanks for all the replies here. I fitted the kit (59600-45811) and it all seems good! Suzuki must have just altered the design for whatever reason. I did some more digging and found posts from a GT750 (shares this part number) forum noting the same thing - the piston is longer than the original but fits and works perfectly fine.

One step forward, two steps back however as when I got home from a test ride the bike was leaking from the sump plug. I removed it today to replace and it pulled all the threads of the sump out with it. So the bike remains off the road again until I can get that sorted :(
 
Not to high jack your thread but I am doing the same thing right now. Can you send me the link to the schematic to put it back together?
Thanks
 
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