rear master cylinder

[dabearded1]

I have searched thru just about every topic on the forum and haven't found what I'm looking for.

I need a rear master cylinder for a 78 xs400 with disc brake. Is there a direct bolt in that will work? A rebuild kit from a local dealer is $97 USD. I'd like to see if there were a cheaper option that will bolt on without any modding or changing the entire braking system.

I also need the gauge cups for the speedo and tach.

When I hooked up the brake light(made a mount out of aluminum stock to get rid of the stock fender) it blows the 10 amp fuse. It was blowing the fuse before it put back on. Before it blows the fuse the brake light stays on like the brakes are being used. I checked the left and right control wires and none are cracked or in need of repair. When the front master cylinder was being put together I noticed a pin that controls the brake switch, it had a spring, black plastic bushing and a copper sleeve. When I assembled it I put the copper sleeve, then plastic piece and then the spring. Was that the proper order? It fell out before I could see how it was arranged when I took it apart.

Thanks in advance for any help.

 

[drewpy]

the brake switch connects live supply, so any earthing will result in a blown fuse.
the master cyl kit part # is 1U4-w0042-50

the m/c assembly is # 1U4-25850-50

google the numbers as you may find shared parts

 

[dabearded1]

Thanks drewpy. I'll Google those part numbers now. I'll check every wire from both brake switches tonight after work.

 

[dabearded1]

So I found a 1978 yamaha parts catalog that lists every part number for every part found on a 1978 xs400. If anyone wants it send me a pm with your email address and ill send it to you

 

[skillzman1]

did you find a part number for the caliper pistons that was still in production/supply?
my caliper pistons are corroded around the seat and likely will leak.

 

[dabearded1]

No I have not. The catalog I found does not list a part number for the piston. Both pistons on this bike are slightly pitted. My uncle is a machinist so I'm gonna talk to him about making me new ones.

Drewpy is aluminum good to use or should it be stainless?

 

[drewpy]

No I have not. The catalog I found does not list a part number for the piston. Both pistons on this bike are slightly pitted. My uncle is a machinist so I'm gonna talk to him about making me new ones.

Drewpy is aluminum good to use or should it be stainless?

stainless is better as you really need to disimilar metals next to each other to prevent corrosion plus the expansion/heat of alu would affect the seals IMHO

 

[dabearded1]

Ok cool. Thanks drewpy.

 

[Icarus]

I just picked one up from the dealer here (Canada) Cost me $61 Bit much for a piston, spring and a couple of rubber cups

 

[dabearded1]

Does that dealership have a website? $61 isn't bad. The rebuild kit without the piston is $35.

 

[dO-bOy]

i paid about 60 for my rear rebuild kit too. better than nothing as there doesn't seem to be a jobber replacement. i was contemplating fabbing mounts for a modern cylinder but they're avery different style