Master Cylinder Rebuild

[Jeff in W.C.]

Moving on to my next project, which is refreshing the front brake system that will include rebuilding the master cylinder. My question is whether or not I need to remove the whole right handlebar assembly or can the master cylinder be removed with the right handlebar assembly still in place. I did some searching and reading, but could not find a definitive answer. The bike: 1988 R100 RT.

[richard t]

I rebuilt my 1991 K75 without removing the handle bars

[Rob Frankham]

You can remove the master cylinder without removing the assembly from the handlebar as long as it's fairly clean an there is no corrosion around the joint... although why you would want to do so I'm not sure.

The master cylinder is attached to the mount by two allen screws accessed from the area on the opposite side of the mount from the lever... that is below the throttle cable terminations. You will need to remove the throttle cables and use a long allan key to get at the bolts and this is particularly fiddly beacause the bars mean you can't turn the key completely and have to turn it a couple of flats at a time. It;s easier if you to loosen the mount on the bars and use a long ball ended allan key but still frustrating. Given that the switchgear can be removed from the throttle mount with one simple screw and the cables will need to be disconnected, it's much easier just to take the whole mount off the bike. You will probably want to clean up the mount anyway so to me it's a no brainer.

Rob

[Jeff in W.C.]

Thanks Rob. I was trying to save a little bit of work. If the bike didn't have heated grips, I wouldn't think twice about removing the right assembly. I remember looking into replacing the throttle heated grip years ago and it seemed more fidgety than I wanted to deal with. I probably should replace the throttle heated grip since the gear portion on the throttle is somewhat worn, and I have the replacement (and cam) just sitting in a box.

[gspd]

I don't recall ever having to remove the whole perch assembly to remove the master cylinder and or heated grip. Depending on the bike you might have to rotate the housing a bit and/or move the throttle cable(s) out of the way. Loosening one allan bolt (accessible from underneath) will allow the housing to rotate on the handlebar to provide better access to the MC bolts if necessary.

[gspd]

it's much easier just to take the whole mount off the bike

With oe heated grips??? maybe not.
To me the easiest way is the fastest way.
I hate disturbing the wiring on any old bike if I don't have to.
The last thing any mechanic wants to hear is " But my old POS heated grip was working when I brought the bike in"

40 year-old heated grip wires are best left alone, or handled with velvet gloves.
Their connectors and wiring are not very robust even when new.

[Rob Frankham]

Heated grips weren't in the equation when I typed the response, however, if you need to replace the throttle tube and gear, you can't do that without disturbing the grip wiring so I still say go for it...

One bit opf advice... don't delay too long in when it comes to replacing the throttle tube. If it feels notchy when you turn it, the next stage is when the gear slips a tooth and you find yourself with a seriously limited throttle range... resetting it normally just results in a repeat performance very soon afterwards. This isn't just irritating, it's also potentially quite dangerous because the tooth slip inevitably tends to happen when the throttle is opened quickly, which is to say very often when you want the power NOW and not getting it can be, to use a euphemism, very embarrasing.

Rpb

[Airbear]

I'll add to Rob's advice above that replacing just the throttle tube and cam gear may not be sufficient to give a smooth and snappy throttle since the 'axle' in the housing and the locating lug in the top cap can also wear quite badly. I replaced the tube and cam in mine and still had a horrible notchy throttle. I put up with it for years before throwing dollars at a whole new perch from Motobins a couple of years ago (mine has the /5 controls). I also put in lighter return springs and the difference is remarkable. It's a definite performance mod.