Triumphrat

blackienig

Me and my buddy are restoring his 76 Bonneville and we are nearly done except for fixing the rear master cylinder. we have the rebuild kit that come with new O rings, but we couldn't figure out how the actual rear master cylinder is removed?? Can someone please explain this procedure for me??? Any info would be greatly appreciated! Thanks

Davie

Hello there!The cylinder is held in place by a small grub screw which will need to be removed by a 1/8"(I think) Allen key,its located on the underside of the alloy housing.It has probably been undisturbed for years so it will be a pig to undo.Soak the whole unit in penetrating oil to hopefully allow easy removal(wishful thinking!).

daveforty

Take note of how far the master cylinder is screwed into it's holder before unscrewing the thing, it is a crucial setting for the thing to work properly.

blackienig

Hmmm i might need to double check the exact year of this bonnie, the rear MC im looking at appear to be one solid body with two bolts running threw it, even with the bolts loose the MC wont budge because the frame makes it impossible to remove the top bolt, thee tire wont allow it fall out and also the metal shaft that links it to the brake pedal doesnt seem to separate either LOL, never had so much trouble working on a bike in my life LOL. If my un professional description doesnt help then i will post the exact year of the bike later, all i know is that its late 70's for sure. thanks for your help.

daveforty

To get the master cylinder off you will have to take the wheel out, undo the nut on the inner end of the brake lever shaft, pull the shaft out (easier said than done if it hasnt been greased). There will be a bang as the coil spring releases and the spring and its spacer will drop away. Then you can get at the nuts which hold the master cylinder to it's mounting plate, or remove the sleeve nut / bushing that supports the brake pedal spindle and remove the mounting plate from the bike with the master cylinder attached.

Various hydraulic pipes will have to be disconnected. Note that the rubber hose to the caliper mounting plate has a stripe printed along it's length, this is to enable you to check the pipe isn't twisted when it is re-assembled, and that the spacer (concentric with the coil spring) is assembled with the recessed side facing the brake pedal. You will need a hook of some sort to pull the coil spring into place when you re-assemble, a piece of welding rod would be a good starting point for making such a tool.

p.s. it's a Bonneville

blackienig

WOW thats alot of crap to take off just to swap a MC LOL, and BTW it is a 76 bonneville. any chance that we can rebuild it while its on the bike?? like Davie suggested?? we just have that little rebuild kit that come with a couple O rings. whats the smartest way to go about this??? Thanks!!!!!

dirtyharry

What Daveforty says is the go. You cannot really o'haul cylinder in place. It needs to be taken off so as you can clean it properly and inspect the bore for rust and wear. No good putting a kit in it if it's worn etc, and it's hard to determine when it's in place. The cyliinder is mounted in the worse place possible as you would already know. The reason i know is because i've done mine, bugger of a job.
Dirty Harry.