Grob 103 Twin II Brake Master Cylinder

What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake master
cylinder, right? Did anyone mention why it needed replacement? My
first
guess is wear or corrosion in the cylinder bore causing it to leak
pressure. If this is the case, there are places that will bore the
cylinder and sleeve it with either stainless steel or brass. It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of doing
that
for an aircraft brake system. And on the Gripping Hand, I would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be done
is
to swap over the lever.

the new master cylinder may not have the brake lever installed.. (attached)
as most replacement motorcycle parts do not either, the master cylinder is
separate part number from the external brake lever handle.

BT

"Mike McCarron" wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake master
cylinder, right? Did anyone mention why it needed replacement? My
first
guess is wear or corrosion in the cylinder bore causing it to leak
pressure. If this is the case, there are places that will bore the
cylinder and sleeve it with either stainless steel or brass. It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of doing
that
for an aircraft brake system. And on the Gripping Hand, I would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be done
is
to swap over the lever.

At 04:50 24 October 2008, BT wrote:
the new master cylinder may not have the brake lever installed..
(attached)
as most replacement motorcycle parts do not either, the master cylinder
is

separate part number from the external brake lever handle.

BT

"Mike McCarron" wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake master
cylinder, right? Did anyone mention why it needed replacement? My
first
guess is wear or corrosion in the cylinder bore causing it to leak
pressure. If this is the case, there are places that will bore the
cylinder and sleeve it with either stainless steel or brass. It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of doing
that
for an aircraft brake system. And on the Gripping Hand, I would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are
talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be
done
is
to swap over the lever.

At 10:15 24 October 2008, Don Johnstone wrote:
At 04:50 24 October 2008, BT wrote:
the new master cylinder may not have the brake lever installed..
(attached)
as most replacement motorcycle parts do not either, the master cylinder
is

separate part number from the external brake lever handle.

BT

"Mike McCarron" wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake master
cylinder, right? Did anyone mention why it needed replacement? My
first
guess is wear or corrosion in the cylinder bore causing it to leak
pressure. If this is the case, there are places that will bore the
cylinder and sleeve it with either stainless steel or brass. It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of
doing
that
for an aircraft brake system. And on the Gripping Hand, I would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are
talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be
done
is
to swap over the lever.






Look on the bright side, at least he isn't in the UK. I'm pretty sure
BMW don't supply brake cylinders with EASA release certificates. I can
imagine:

1. Brake cylinder from BMW: £100
2. Identical BMW brake cylinder the man from EASA has sprinkled magic
pixie dust on: £350
3. ??????
4. Profit

On Oct 24, 4:30*am, Andrew Warbrick
wrote:
At 10:15 24 October 2008, Don Johnstone wrote:



At 04:50 24 October 2008, BT wrote:
the new master cylinder may not have the brake lever installed..
(attached)
as most replacement motorcycle parts do not either, the master cylinder
is

separate part number from the external brake lever handle.

BT

"Mike McCarron" *wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake master
cylinder, right? *Did anyone mention why it needed replacement? *My
first
guess is wear or corrosion in the cylinder bore causing it to leak
pressure. *If this is the case, there are places that will bore the
cylinder and sleeve it with either stainless steel or brass. *It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of
doing
that
for an aircraft brake system. *And on the Gripping Hand, I would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are
talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be
done
is
to swap over the lever.

Look on the bright side, at least he isn't in the UK. I'm pretty sure
BMW don't supply brake cylinders with EASA release certificates. I can
imagine:

1. Brake cylinder from BMW: £100
2. Identical BMW brake cylinder the man from EASA has sprinkled magic
pixie dust on: £350
3. ??????
4. Profit

After replacing the master cylinder on our ship we found that the
problem was with the brake line linking the two cylinders. When we
replaced it the problem of poor braking was solved. Must have been
unobservable expansion within the OE line!

Where did you find a brake line to purchase that would fit the Grob?

Mike

At 12:42 24 October 2008, haven wrote:
On Oct 24, 4:30=A0am, Andrew Warbrick
wrote:
At 10:15 24 October 2008, Don Johnstone wrote:



At 04:50 24 October 2008, BT wrote:
the new master cylinder may not have the brake lever installed..
(attached)
as most replacement motorcycle parts do not either, the master
cylinder
is

separate part number from the external brake lever handle.

BT

"Mike McCarron" =A0wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake
master
cylinder, right? =A0Did anyone mention why it needed replacement?
=
=A0My
first
guess is wear or corrosion in the cylinder bore causing it to
leak
pressure. =A0If this is the case, there are places that will bore
th=
e
cylinder and sleeve it with either stainless steel or brass.
=A0It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of
doing
that
for an aircraft brake system. =A0And on the Gripping Hand, I
would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are
talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be
done
is
to swap over the lever.

Look on the bright side, at least he isn't in the UK. I'm pretty
sure
BMW don't supply brake cylinders with EASA release certificates. I
can
imagine:

1. Brake cylinder from BMW: =A3100
2. Identical BMW brake cylinder the man from EASA has sprinkled magic
pixie dust on: =A3350
3. ??????
4. Profit

After replacing the master cylinder on our ship we found that the
problem was with the brake line linking the two cylinders. When we
replaced it the problem of poor braking was solved. Must have been
unobservable expansion within the OE line!

At 13:45 24 October 2008, Mike McCarron wrote:


Where did you find a brake line to purchase that would fit the Grob?

Almost any motorcycle shop will make one up for you. If you get one that
has a steel braid outer you will, as a previous poster said, get rid of
the problem of brake line expansion. I have to say that while brake pipe
expansion is a problem with mootor cycle brakes, given the very short line
on the Grob I am surprised that was a problem.

On Oct 24, 6:45*am, Mike McCarron wrote:
Where did you find a brake line to purchase that would fit the Grob?

Mike

At 12:42 24 October 2008, haven wrote:

On Oct 24, 4:30=A0am, Andrew Warbrick
wrote:
At 10:15 24 October 2008, Don Johnstone wrote:

At 04:50 24 October 2008, BT wrote:
the new master cylinder may not have the brake lever installed..
(attached)
as most replacement motorcycle parts do not either, the master
cylinder
is

separate part number from the external brake lever handle.

BT

"Mike McCarron" =A0wrote in message
...
What do you mean by "swap over the lever"?

Mike

At 22:00 23 October 2008, Don Johnstone wrote:
At 13:00 23 October 2008, Jim Beckman wrote:

This thread started with the necessity of replacing the brake
master
cylinder, right? =A0Did anyone mention why it needed replacement?
=
=A0My
first
guess is wear or corrosion in the cylinder bore causing it to
leak
pressure. =A0If this is the case, there are places that will bore
th=
e
cylinder and sleeve it with either stainless steel or brass.
=A0It's
done
all the time for old cars.

On the other hand, I don't know anything about the legality of
doing
that
for an aircraft brake system. =A0And on the Gripping Hand, I
would
probably
do it that way myself.

Jim Beckman

Old cars normally have steel brake cyliders, the BMW part we are
talking
about is aluminium. Putting a steel or brass sleeve in will almost
certainly cause corrosion (disimilar metals).
A new part is available and is not expensive. All that needs to be
done
is
to swap over the lever.

Look on the bright side, at least he isn't in the UK. I'm pretty
sure
BMW don't supply brake cylinders with EASA release certificates. I
can
imagine:

1. Brake cylinder from BMW: =A3100
2. Identical BMW brake cylinder the man from EASA has sprinkled magic
pixie dust on: =A3350
3. ??????
4. Profit

After replacing the master cylinder on our ship we found that the
problem was with the brake line linking the two cylinders. *When we
replaced it the problem of poor braking was solved. *Must have been
unobservable expansion within the OE line!

As I remember, it came from Grob in Bluffton, OH but now they are out
of the parts supply business ?!

Everyone has covered the topic well but I'll add my 2 cents having
repaired our 103 brake. Yes, it is a Magura master cylinder as used
on BMWs. All they did was cut off most of the brake lever and mount a
cable to the stub to actuate it. Yes, bleeding from the bottom of the
system (slave) works best. Here's a little trick - any marine supply
depot sells a plastic pump for replacing bottom end oil in outboard
motors. It looks like a shampoo or epoxy pump and screws onto a
standard oil, or coincidentaly, brake fluid bottle. Screw it on the
bottle, push the tubing onto the cracked open caliper bleed nipple and
pump slowly. It forces the brake fluid up. Have someone at the
master cylinder with a towel wrapped around it to take care of
overflow. It is always easier to force air bubbles upwards in a
hydraulic system then to force them downwards. It is faster then from
the top and a whole lot let frustrating.

Another hint ... don't worry about replacing the entire master
cylinder, Just go into a BMW motorcycle dealer and buy a rebuild kit
(about $75). It includes a new piston, spring and seals. (I can't
recall the bore size but these kits care reasonably universal - all
you need to do it confirm the size at the parts desk.) Use a very
fine emery cloth or wet sandpaper to gentle hone the cylinder and put
it all together. Usually the problem is the seals, not pitting of the
cylinder. Total job takes about 1.5 hours including removing and
replacing the cylinder.