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Old October 17th, 2016   #1
PaulRB
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Default F-Master Cylinder - Old Bikes

I've got a front brake master cylinder problem with the YellowWing.
To make a long story short I've decided to up-grade the front master cylinder to modern spec Nissin equipment.

I've run a 3 braided line system for 20 years with the manifold installed primarily to retain the brake light switch.
Stock 40 year old master cylinder.
The new Nissin master cylinder has it's brake light switch on-board and would allow me to either disregard it and retain the manifold or remove the manifold use the Nissin switch and go to a 2 line system using a dual line banjo bolt.

Questions for anyone that has a old bike dual disk front brake system.

Are you using a three line system or have you gone to a two line system?
Noticeable difference between the two systems?

My concern is turning a three line system that already has way more braking ability that it has tire to use it, into a two line system where serious braking ability becomes for lack of a better word a problem.
There is only so quick you can stop a 110/90-19 front tire even with current tire compounds Michelin employs on the Pilot series.
Larger tire is not an option.

The new Nissin Master Cylinder.
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File Type: jpg Brake Master Cylinder.jpg (8.4 KB, 44 views)
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Old October 17th, 2016   #2
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Default Re: F-Master Cylinder - Old Bikes

Is the diameter and stroke of the new master cylinder the same as the old one? If it's smaller diameter it will take less hand effort to generate more pressure in the system but you may need more stroke to move the same volume of fluid. If you have a larger diameter piston in the master, it will require more hand force/effort to generate the same amount of pressure as the old one, but a shorter stroke is needed to move the same volume of fluid.

Unless they create some kind of obstruction or are too flexible (i.e. inflate too much) the lines do not affect the pressure in the system, all other factors being equal. It's really all about the ratio between the master and slave cylinder diameters.
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Old October 17th, 2016   #3
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Default Re: F-Master Cylinder - Old Bikes

Quote:
Originally Posted by Wjbertrand View Post
Is the diameter and stroke of the new master cylinder the same as the old one? If it's smaller diameter it will take less hand effort to generate more pressure in the system but you may need more stroke to move the same volume of fluid. If you have a larger diameter piston in the master, it will require more hand force/effort to generate the same amount of pressure as the old one, but a shorter stroke is needed to move the same volume of fluid.

Unless they create some kind of obstruction or are too flexible (i.e. inflate too much) the lines do not affect the pressure in the system, all other factors being equal. It's really all about the ratio between the master and slave cylinder diameters.
All has been taken into consideration.
This caliper is said to be the "go to" unit for the GL1000 replacement.
Piston size 11/16 (stock) vs 5/8 (new)
M/C to caliper ratio 9.47 (stock) vs 11.46 (new)


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Old October 17th, 2016   #4
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Default Re: F-Master Cylinder - Old Bikes

Caliper or master cylinder? If you mean master cylinder it looks like those ratios are pretty close though the replacement will require nominally less hand lever squeeze than the original to generate the same braking force. Should lend a more responsive feel.
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Old October 17th, 2016   #5
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Default Re: F-Master Cylinder - Old Bikes

Quote:
Originally Posted by Wjbertrand View Post
Caliper or master cylinder? If you mean master cylinder it looks like those ratios are pretty close though the replacement will require nominally less hand lever squeeze than the original to generate the same braking force. Should lend a more responsive feel.
Master Cylinder 5/8"
Caliper pistons are 38mm. Newly installed.
Same as the old simply stainless steel.
New seals, boots, dust covers.
Moves to DOT 4.
Total rebuild.
The stock master cylinder has what is described as a "wooden feel".


M10 x .145 - Aluminum Crush Washers - Banjo Bolts & Coolant Drain.
Bag of 50 $20.00 Delivered
boltmotorcyclehardware.com

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Old October 17th, 2016   #6
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Default Re: F-Master Cylinder - Old Bikes

Quote:
Originally Posted by PaulRB View Post
The stock master cylinder has what is described as a "wooden feel".
Paul
So the changed ratio and new parts/lines should help that a lot. Sometimes however, there's just too much flex in the caliper itself to really solve that wooden feel, especially calipers with the two halves bolted together.

Brembo's "monblock" calipers, machined from a single billet, rather than bolted up, are designed to avoid this problem.

Sounds like a fun project, let us know how it all works out.
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Old October 20th, 2016   #7
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Default Re: F-Master Cylinder - Old Bikes

Although this thing does have calipers that are bolted together like everything in the 70's overkill was not a design flaw it was a underrated design enhancement.
The calipers are massive blocks of aluminum precision machined, drilled and threaded with the finest 8mm bolts of the day holding it together and warding off the flexy flyer syndrome of the 70's.
Don't I wish.

New Master Cylinder installed and system bleed.
Still on the lift as a slight weep at the outer crush washer of the banjo bolt appeared last night.
A quick look at the torque, we are given a range of 18-22ft-lbs and a increase to 20 looks to have stopped the weep.
Since this thing resides over my beautiful Yellow paint a day of paranoia and a squeeze of the lever every time you walk by is called for, diaper still installed at this point.

Just sitting on the bike making vroom, vroom noises and squeezing the lever I can already tell of a significant change in feel.
It's not the toggle switch on or off feel any more, feels a lot like the ST, vroom, vroom noise on it as well.

If the diaper shows no sign of weeping, I will actually finger it as well, in the morning the vroom, vroom noises will be replaced with actual motor sounds of a freshly tuned, fresh belted, new blue coolant equipped zoom about.


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Last edited by PaulRB; October 20th, 2016 at 02:26 PM.
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Old October 21st, 2016   #8
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Default Re: F-Master Cylinder - Old Bikes

Actual motor sounds confirm what I already knew.
The timing belt change part of the program was good.
The 20 ft-lbs torque on the banjo bolt stopped the weep.
Test ride went well.
Actual stopping power with feeling in the lever.
Does not look original but function over rules style.


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