Can't bleed xj750 seca brakes

Hey, so I have a 1982 seca 750 that I can't bleed the brakes

PHOTO ATTACHED

When I Pull the lever in the little rod that enters the master cylinder (the one in the photo that the cable is attached to) goes in but the thing inside the master cylinder that the rod pushes on doesn't return out when I let go of the lever and the rod is no longer touching it.

Is there a spring or something in there that might be seized?

How difficult is it to take apart or replace does anybody know?

 

I am having the same issue. I have pressure at all the air bleed locations just fine, but the MC will not pressurize enough for the brakes to engage. I will be trying the reverse bleed method soon. Very frustrating indeed.

 

Well let me know if you manage to get them working, I'll have to try the reverse bleed too

 

Did you rebuild the master cylinder? If nto, when was it last done? If you don't know, you probably have to bite the bullet. Yes, there's a return spring in there. I tried rebuilding mine using a partial kit/not replacing the return spring. That could have killed me. RE-rebuilt with the full kit, (and also honed out the bore) and all's well.

The return port for the fluid is MICROSCOPIC on these. Them getting gunked up and not returning pressure to the res. is absolutely common. Search threads, many on 'tricks' to bleed the brakes. But if the spring should be returning the piston smoothly.

 

Yeah I was taking a further look at the MC today and I'm 99% sure it's the spring in it,

How did you manage to take the spring out of the MC?

I'm having trouble taking it apart.

 

There's a circlip under the rubber boot. If it's really hanging up, a LOW PRESSURE burst of air from the top of the MC (where the metal tube screws in, not the reservoir) should knock it loose, but be VERY careful about launching/losing/being impaled by parts. This really needs to be done off the bike, as much of a PITA as that prospect is. After taking mine off and back on a few dozen times over the last couple years, I've got it down MOSTLY swear-free.

 

Wanted to add: pay CLOSE attention to the order and orientation of parts so you don't put the plunger or diaphragm in backwards. Again, if you don't know when the MC was last touched, I highly recommend the full rebuild kit from Len. NOT CHEAP, but they're your front brakes, man.

 

OK thanks mate, I'll try this soon .