Under the Tank Master Cylinder
Posted: Wed Jun 08, 2016 3:07 pm
Most of my airheads are of the /6 and /7 series, which means that I, like everybody, am going to have problems with leaky master cylinders--and I do! Usually the problem is pitting of the bore, especially around the rear seal. I've had some successes in honing out the cylinder bore, but not always successful in the long run. Currently, as I've mentioned, I'm in the process of putting on some new smoked red body work and the bike is starting to look gorgeous. But back to master cylinders. What I would really like to find is somebody who will bore my old master cylinder and then reline it, preferably with stainless steel. I know it is common in the brit bike world to re-sleeve the carb where the slides moves up and down. A similar fix would seem to be ideal for under the tank master cylinders. Heard of anybody who does that?
Now, my question asked, I'll do a bit of meandering. First of all the BMW overhaul kit for under tank master cylinders is (or at least always was) expensive as hell. I seem to recall that a few years ago the kit was well over $50 and will surely be significantly more now. You get a lot of parts in the kit, but the only ones usually needed are the plunger seal and the seal at the back of the bore.
I am open to buying a handlebar mounted master cylinder, but that introduces certain other problems to be dealt with. For example, Air Bear, put one on his bike and it looks (and apparently) works just fine. But his /6 has the early /5 type switch gear rather than the later switch gear that my bikes have. Plus there are other issues such as devising a splitter between the master cylinder out put to the two ATE 'swinging' calipers. Then there are other issues to be dealt with such as is there two throttle cables exiting the throttle (one for each carb) or is there a single throttle cable coming out and then going to a splitter under the tank to actuate two carbs. (Which latter concept I abhor!) Then, also, depending upon the years involved the throttle cam can be different gearing from the old one, requiring $$$ that I would rather spend on something else.
I seem to remember that Motobins has, or had kits, that you can buy with a lot of money.
(By the way, Duane, I'm purposely choosing to go here first in lieu of the internet for my info. Call me obstreperous!)
(Incidentally, the bike that's getting the new clothes is the one you see me straddling on my avatar.)
Ken
Now, my question asked, I'll do a bit of meandering. First of all the BMW overhaul kit for under tank master cylinders is (or at least always was) expensive as hell. I seem to recall that a few years ago the kit was well over $50 and will surely be significantly more now. You get a lot of parts in the kit, but the only ones usually needed are the plunger seal and the seal at the back of the bore.
I am open to buying a handlebar mounted master cylinder, but that introduces certain other problems to be dealt with. For example, Air Bear, put one on his bike and it looks (and apparently) works just fine. But his /6 has the early /5 type switch gear rather than the later switch gear that my bikes have. Plus there are other issues such as devising a splitter between the master cylinder out put to the two ATE 'swinging' calipers. Then there are other issues to be dealt with such as is there two throttle cables exiting the throttle (one for each carb) or is there a single throttle cable coming out and then going to a splitter under the tank to actuate two carbs. (Which latter concept I abhor!) Then, also, depending upon the years involved the throttle cam can be different gearing from the old one, requiring $$$ that I would rather spend on something else.
I seem to remember that Motobins has, or had kits, that you can buy with a lot of money.
(By the way, Duane, I'm purposely choosing to go here first in lieu of the internet for my info. Call me obstreperous!)
(Incidentally, the bike that's getting the new clothes is the one you see me straddling on my avatar.)
Ken