Master Cylinder Swap - Help!

[markd]

I have a 1wg (88) fzr400. My front master cylinder failed. I have an 03 cbr600 master cylinder, and an R6 master. Are these compatible with the 2 pot calipers on my 1wg or will they move too much fluid? How do I find out the bore on master cylinders? And what is the proper ratio between cylinder bore and piston diameter?
I am racing this bike, so looking for best braking option. Eventually going to swap for 90 fork lowers and go with R6 calipers, so if the R6 master is compatible with the 88 2 pot calipers, I would prefer to go with that, but don't want a master cylinder with too much advantage.

Thanks!

Mark

[ragedigital]

They should work without any issue to my knowledge. Most people, including myself, have swapped MCs and have had nothing but the best outcome. The new ones should have some adjust ability to them as well.

If you're racing, then make sure you're also running stainless steel brake lines.

[markd]

Already running the ss lines. So you don't think I'll have any issue with modulation if the master cylinder is different size? Thanks!

[yamaha_george]

Already running the ss lines. So you don't think I'll have any issue with modulation if the master cylinder is different size? Thanks!

MD,
OK let me see if I have this straight :-
at this moment you have single opposed calipers and the m/c has failed?
if you go with the R6 m/c the hydraulic advantage will make for very fast braking BUT when you swaap to new forks with twin opposed brakes the will be great.

Now I know I am gonna get a lot of flack for this so here goes you do the R6 m/c swap and NOT completely bleed the system .

NOT exactly safe in racers 101 but I have done it after arace crash and borrowing a M/c for the next race.

How much you leave them spongy is upto you and your style of riding, if you bleed them totally just be aware that grabbing a handful in a panic WILL SPIT YOU off for sure unless you know how to do flying W's at ??mph.

BE warned OK the rest is your call.

[sweekster]

The r6 master should work with those calipers.

[markd]

Thanks George,

Getting insta-lock on the brakes was exactly what I was afraid of. A little worried about leaving them spongy, as when they do grab they will grab hard, right? Don't want nothing,nothing,nothing, BRAKES!

Does the 03 cbr600 master have more or less hydraulic advantage than the R6? (from the blue spot caliper years)

How can I tell how much hydraulic advantage a mc has? It is by the bore size/stroke, right? How do I measure that?

Then how do I determine the right size mc for particular calipers?

Thanks!

[ragedigital]

Then how do I determine the right size mc for particular calipers?

That's easy... use the stock MC.

Most newer MCs have a way to adjust them. I would bleed it correctly and try it. Chances are it won't be all or nothing. It might actually be what you prefer for racing.

[markd]

It's easy to use the stock, but I was looking for a way to determine which of the extra mc's I had would work better, not buying another stock one that is 20+ years old. Also, wondering the ratio so I can figure this out in future cases, and determine which mc would be an improvement and which would have too much advantage.

[yamaha_george]

It's easy to use the stock, but I was looking for a way to determine which of the extra mc's I had would work better, not buying another stock one that is 20+ years old. Also, wondering the ratio so I can figure this out in future cases, and determine which mc would be an improvement and which would have too much advantage.

Hi,
As I said it is the level of bleeding that will say how the brakes re-act it will be progessive as the air compresses no nothing then all.
There is a master cylinder chart called some thing like the " the vintage brake company" that has a great explanation of ratio etc and how to measure them Ijust did a quick search but I will look again.

EDIT:-
http://www.vintagebrake.com/mastercylinder.htm


NOW in the TECH WIKI

[markd]

Thanks George!

Just what I was looking for!

[yamaha_george]

Thanks George!

Just what I was looking for!

Yuppppp, the old Geezer strikes again

[pefrey]

The only problem is that is does not tell you the bore of the master cylinder you have. I've tried searching for that information for stock MC's on current bikes and had very little luck.

The easiest solution is also the hardest, try it and find out.

EDIT: I'm attaching two links. The "HEL" link is especially good.

http://www.h-e-l.co.uk/brake-doctor/

http://motorcyclebloggers.com/tech-talk ... cylinders/

[RoadDogma]

R6 master cylinder is 14mm, giving an area of 154 sq. mm. Since the original poster is interested in using the MC with 2 pot FZR calipers, I measured the piston diameter of an '89 FZR400 caliper and got 42mm yeilding 2770 sq mm per caliper. Thus, the R6 MC paired with 2 dual piston FZR calipers gives a ratio of 36:1.

Compare this to R6 calipers. Each caliper has two 30mm pistons and two 27mm pistons for a total of 2558 sq mm per caliper. Thus the stock ratio between the R6 MC and two R6 callipers is 33:1. I know this does not account for leverage ration provided by the lever pivot point, but I hope it helps.

[markd]

Just got back from a test day at the track. The R6 mc works great with the 88-89 2 pot calipers. It was a little grabby at low but at track pace they were great. MUCH more stopping power, while still having good feel for trail braking fairly deep. I'm guessing the stock mc was under powered for the calipers, since this is so much better without being on/off. Thanks all for the help!

I am also interested in how to find out the bore of particular mc's if anyone knows. Also, does the stroke of the mc piston affect the amount of fluid pushed? Would this be controlled by the lever pivot point thus adjustable?

[yamaha_george]

Just got back from a test day at the track. The R6 mc works great with the 88-89 2 pot calipers. It was a little grabby at low but at track pace they were great. MUCH more stopping power, while still having good feel for trail braking fairly deep. I'm guessing the stock mc was under powered for the calipers, since this is so much better without being on/off. Thanks all for the help!

I am also interested in how to find out the bore of particular mc's if anyone knows. Also, does the stroke of the mc piston affect the amount of fluid pushed? Would this be controlled by the lever pivot point thus adjustable?

The volume of fluid moved is dependent on stroke & bore "the feel" of how much effort you put into stopping the bike is by lever ratio and most modern lever sets are now adjustable for hand span & that "feel"

As has been said info on what model has what BORE and what STROKE is singularly hard to find

IF any one has any details on these facts related to Model we can start our own table of details on the WIKI and stop this drought on M/C details.