Front master cylinder question

[Skinner]

I just received a new OEM piston and cup assembly for the front master cylinder on my 1982 Katana 750. It shares this part with the 1982 and 1983 GS1100E's and ES's, along with the 1983 GS650M. When I removed the old piston and cup there was no o-ring installed anywhere, but there is one included in the new kit - see pic, 2nd column from the left, under the piston. I'm thinking that it goes on the round piece with the square top (3rd column from left, 2nd item) - can anyone confirm? All the parts drawings that I could find online were inconclusive.

[Nessism]

Yes, you have it correct.

[Skinner]

Yes, you have it correct.

Thanks Ed. It's odd that there was no o-ring on that piece when I disassembled the MC. I would have expected a leak.

Cheers!
K

[boxter-99]

Guys i have a GS1000G 1980 shaft 8-valve. Anyone knows if the OEM front master is good enough or I should use the 16mm Chinese copy?
Anyway I want to rebuild the OEM front master . I bought a GS1000 rebuild kit from ebay. In it there is a spring with a rubber in one of its ends.
I am not sure where the "rubber end" of the spring goes.
Does it goes:
1) To the end of the bore of the main body of the front master (next to the hole of the banjo bolt)
2) Or faces towards the master cylinder piston
(meaning that the completely "naked part of the spring" points towards the end of the bore inside the front masters's main body, next to the hole of the banjo bolt)

Anyone knows?

Many many tthanks,

[mmattockx]

I am not sure where the "rubber end" of the spring goes.

The rubber goes against the face of the piston.


Mark

[boxter-99]

Mark, many many thanks for the reply, I have now rebuild the front master
However I am unsure what to use. I want really good front brakes but ... I dont want to lock the front (I have upgraded to progressive fork springs)
Do you think the OEM front master is OK combined with stainless hoses?
There is also a Chinese alternative with metal box reservoir which I found on ebay and some ppl here they have used and saying its OK.
And of course I can use a later model front master from a CBR1000 or an R1 2015 or even a fully adjustable Brembo RCS19
But that will spoil the vintage look! I am using stock (fully rebuild) front calipers but Brembo pads and discs.

Many many thanks,

[mmattockx]

Mark, many many thanks for the reply, I have now rebuild the front master
However I am unsure what to use. I want really good front brakes but ... I dont want to lock the front (I have upgraded to progressive fork springs)
Do you think the OEM front master is OK combined with stainless hoses?

You need to be able to lock your wheel in order to have enough stopping power for emergencies. A brake system that is incapable of locking the wheel is dangerous. Braided stainless lines will be just fine with your rebuilt m/c and you will almost certainly come to appreciate the firm lever feel and improved performance of the upgraded system.


Mark

[boxter-99]

Hi,
Many thanks for the answers.
May I also ask is it natural for the front caliper outer parts to be moving while you press the front brake lever?
There is 3 hoses system in the front brakes (all stainless) one comes from the master cylinder and then splitting under the bottom fork yoke towards the calipers
However it seems to me that the caliper that its brake hose is next to the one that comes from the front master cylinder (right caliper same side as front master cylinder) ) is flexing a bit more than the other side caliper (left caliper) that its brake hose is on the other side of the hose splitter. Is that normal?
Also pressing the brake lever (oem front master) seems to have quite a travel (eg comparing with a superbike) Is that normal?
Finally I run bridgestones anyone knows what are correct pressures for good stable braking?

[boxter-99]

For some reason one of my front calipers, the right one, moves too much and from time to time the front lever goes very soft and touches the throttle grip. But if you pump it a bit it comes back. Still is very soft.
If you look on the right caliper while you pressing the front brake lever you can clearly see it moving way too much around (outwards).
No idea why. Pads are Brembo new. Same as discs. Is this is a problem of the caliper or of the rebuild front master?