how big of a master is needed

ok guys im doing the handle bar mount MC for the 750 seca, im getting mixed up lol

what size bore is needed for this to work, i hear 14mm (5/8) and then i hear its to small. i lost an auction on an xs1100 (11/16) master last night unfortunatly.

the r1 and r6 masters are 14mm are they not? and i hear of people using those.

Has anyone used all the "ebay" masters 16x18 radial master cylinder or something or other, any work on how good they are

 

Have you looked and Mikes XS? New is better than used and not too expensive.

 

Schnarr, a 14mm master will work just fine on a dual-disc XJ-series bike, that's what all of the factory m/c's were on the dual-disc bikes.

We have an aftermarket "original XJ-style" handlebar-mounted, 14mm bore master that will work on your 7/8" diameter handlebars; but be aware, the handlebar covers will have to be modified or eliminated, and the cover mounting "tab" that just in-bound of the right-side control switch will have to be removed and ground flush in order for the master cylinder to sit on the handlebars correctly. In fact, if you remove the bar "covers", then there's a number of the cover mounting "tabs" that will be visible on the handlebars, and which you may want to remove. Be aware that the 750 Seca handlebars are not always fully or nicely chromed as typical handlebars are, since they were never intended to be an "exposed", visible part like on other bikes.

 

no worries my bike is running standard 7/8's euro bars right now.

i was going looney because i read in a few places on the forum that 14mm wasn't big enough for the seca. i found it hard to believe that 14mm could stop a busa but not a seca lol.

thanks SOOOO much chacal 14mm gives me so much more to look at


im thinking fj1200 master

 

chacal are you sure?
i have 11/16 bore master cylinder on my seca. dual discs. thats over 17mm right?

 

Venlis, you're right........I should have said 16mm (5/8") rather than 14mm (9/16").

 

but wait i have a kwak 636r 14mm master cylinder and i also was troubled if it would cut it and because of the posts here about 14mm being insufficient i almost forgot about it. this thread suggests it would be fine?
my master cylinder is bigger than most of yours or what?

whats the score you know than me of these things

 

I think the master cylinder "size" is really a function of two different things.....the fluid capacity of the reservoir and the rest of the system, as well as the size of the piston bore. And those two factors are determined by how big the caliper pistons are, how much fluid is used to displace them to their maximum amount, etc.

 

i aggree with chacal one thing you have to remember some of the bikes use 6 piston calipers if im correct it should take less fluid to move those then a duel piston caliper.bigger bore flows more if im correct but dont hold me to that

 

i have a 14mm from ebay on a maxim and a older gsxr one on a seca
both dual calipers both work fine
think about if the one your looking at will fit with the original switch pod
you will be cutting off the seca's bracket that held the lever and cable

 

looking at the ratio charts on the other page my seca has 9,47 ratio with the oem setup, and with my planned 14mm master upgrade id hit a ratio of 14,73.
the guy says the ratio should be over 23 for a nice brake feel. that would mean i need to get a 11mm master. whats the logic here?
my brakes did feel very woody with my stock 11/16 master.
time for some empiric testing

 

Venlis, part of the "woody" feeling with the 750 Seca front brakes is the cable-actuated master cylinder.........it just feels "funny" or different than what you'd normally expect, probably because the cable stretches as you apply the brakes, and the stretch probably intensifies as you apply more pressure.........in effect, the cable removes most of the "feeback" you get through the hand lever that you normally associate with a brake system on a "traditional" bike braking system........

In reality, the 750 Seca models should really have the "firmest" brake system of all the XJ bikes, as they use steel piping for all but the caliper lines (a mushy anti-dive system doesn't help, though.....).

Prototype pictures of the 750 Seca models actually shows the caliper lines to be mostly rigid steel tubing, also.....something that didn't make it to production.

Perhaps all that rigid steel tubing was "planned for" in that system in an attempt to compensate for the mush feeling that a cable-operated master cylinder was likely to/known to provide.

It's like making your brakes feel like your clutch.......

 

youre right chacal, i think the oem front brake setup is way too complicated, and the cable system definitely reduces the brake feel and strength..

im going to do the brake mod in a few days or weeks, when i get the right handlebar or clipons to fit the m/c. finding a clubman bar that im after seems an impossible task here in finland. i found really nice looking moto guzzi replica clipons that might fit....

 

i ended up running a 16mm 5/8's fj1200 master with SS lines direct from master to calipers, with blocked off anti-dive

this thing will stoppie with 2 fingers on the lever, only thing i notice is i need a stiffer spring up front to supplement the better braking and stiffer springs out back

 

schnarr you think you could try to fix the anti dive back to work first? clean it up and post results.. i would love to hear if it makes a real difference with better brakes!

im trying to figure out if i should do what you did or do what i suggest you to do.

 

i could easily put the anti dive back together but i really don't want it there( if it was a superior technology you would see it on sport bikes now a days) if i were to put it back im sure it would still brake great but with a little less droop in the front when i come on it.

unfortunately these bikes were not stiff enough in the front from the factory and 29 years of sitting on those springs isn't helping lol

i was thinking of running a heavier fork oil but i figure if im going through all the trouble of changing fork oil then i may as well do some stiffer progressives up front.



I have ZERO regrets about doing this mod, all the mods i did this winter it was my favorite. Anything you want to see you can check out my build thread it has most of my pics