are Undertank MASTER CYLINDER crush washer seal, or pipe thread ?

[gtgt_bangbang]

the undertank brake master cylinder has a pressure switch on end , to operate the brake light.
('78 R100 , https://shop.maxbmw.com/fiche/DiagramsMain.aspx?vid=51651&rnd=09082020, BRAKES 34_ 0606)


Several references indicate this pressure switch requires a crush washer to seal it on master body.

Although the Maxbmw DIAGRAM doesn't show a crush washer, they list a seal ring (10 x 13.5 . aluminum) for use with that switch.

I assembled mine with crush washer, expecting switch to crush against it, but the switch's threads bottom out a couple mm before engaging the washer,
as if the switch is taper pipe thread. . I dont recall what the assembly was like before rebuild .....

QUESTION - any one have some info on this ?

Does YOUR undertank master cylinder use a crush washer or it is (self-sealing) pipe thread ?

Rather not fill the brakes with fluid just to find out if it leaks on new frame paint !

thanks in advance

 

[20774]

I'd check Brook Reams website.

 

[melville]

the undertank brake master cylinder has a pressure switch on end , to operate the brake light.
('78 R100 , https://shop.maxbmw.com/fiche/DiagramsMain.aspx?vid=51651&rnd=09082020, BRAKES 34_ 0606)


Several references indicate this pressure switch requires a crush washer to seal it on master body.

Although the Maxbmw DIAGRAM doesn't show a crush washer, they list a seal ring (10 x 13.5 . aluminum) for use with that switch.

I assembled mine with crush washer, expecting switch to crush against it, but the switch's threads bottom out a couple mm before engaging the washer,
as if the switch is taper pipe thread. . I dont recall what the assembly was like before rebuild .....

QUESTION - any one have some info on this ?

Does YOUR undertank master cylinder use a crush washer or it is (self-sealing) pipe thread ?

Rather not fill the brakes with fluid just to find out if it leaks on new frame paint !

thanks in advance

It's a 1/8" tapered pipe thread on the ones I have on hand. 1975, 1978, and 1979 if that makes a difference.

 

[gtgt_bangbang]

It's a 1/8" tapered pipe thread on the ones I have on hand. 1975, 1978, and 1979 if that makes a difference.

thanks, yeah it felt like a good pipe-pipe thread at fit up, so good to know.
First thing that seemed odd was the washer still dangling free after I wasnt going to torque-ture it any more

so anyway I got a NOS trick copper orange crush washer along for the ride, in case aonther bike needs one

 

[pglaves]

At least it isn't a tapered fitting threaded into plastic like on the late recalled fuel pumps of ill repute. I don't understand engineers that thread a tapered fitting into a fragile part. The intern must have been in charge during Oktoberfest or something.