Which front M/C to use to delink XJ brakes?

[BillyRok]

I want to de-link the front and rear brakes on my XJ so the front master cylinder operates both front discs. After reading some old threads I still have a couple questions.

The XJ factory front M/C has a 12.7 mm or 1/2 inch piston correct? Is this sufficient to operate both front discs if using SS rather than the original lines or do I need something beefier? Is anybody currently running a set up like this (de-linked with factory M/C) and are you happy with it? My research says that all the XS front M/C are no longer available...does anybody know the piston size in those?

I did find that an old Virago 920 M/C is still available...4G0-25850-01-00 but it runs about $225. This ran a dual disc system, would this be a better choice? There are a few on Ebay right now but most look pretty beat up.

The joint from the M/C to the discs on the XS is still available for around $30, 1J7-25885-01-00, so I would need one of these also?

Another consideration is whether my right side mirror will thread down into a different M/C.

Thanks for your thoughts.

[bikerphil]

An XS11 front master is 11/16 bore designed for dual caliper. Left hand threads for the mirror mount. There are used ones on Ebay. The 1/2" bore is too small for dual disk.

[crazy steve]

I'm doing just that to my project XJ. I simply got front and rear master cylinders and brake lines from a XS11 Special. To get around the mirror mount issue, I used a XS11 clutch perch also. Except for the lines, all these parts will have to be used but rebuild kits for the masters are readily available.

If you go to a different front master, you do have to watch bore size. Typically, the dual-disc fronts use a 11/16" bore master; you can go as small as 5/8" (16mm) but expect longer lever travel and you really should have stainless braided lines.

[bikerphil]

PartsNmore has a new 5/8 bore Magura M/C that will fit our bikes for $90, P/N 08-0264... Mikes XS also carries the same line.

Edit: MikesXS P/N 08-0265...

http://www.mikesxs.net/products-71.html#products

[mack]

I've used the

Mikes XS one twice now and they work great. However you will need to change the y to a 79 special style to pick up the two lines from both front calipers and run one line from it's top to the m/c. Remove all the surplus lines from the rear m/c proportioning valve to the the front. I hated the whole idea of that system as well. Go stainless when you convert. "Russell" has them off the shelf in the size and lenghts required. Also at the y you'll need a double banjo bolt and three new brass compression washers.

[TomB]

Using the XS1100 11/16" master cylinder on an XJ1100 to make both front rotors work together is not a good idea!

The XJ1100 uses smaller calipers than nearly all XS1100's, the only XS1100 that uses the same calipers as the XJ1100 are the Euro/Japanese market Sport (5K7). The Sport uses a 5/8" master cylinder for dual front rotors so this is the size to use on an XJ1100 with dual front rotors. And the good thing about that is its the most common size M/C used of other bikes.

Using the 11/16" master cylinder on a bike with smaller than standard XS1100 calipers will result in very "wooden" feel to the brake lever DAMHIK




.

[crazy steve]

The XJ1100 uses smaller calipers than nearly all XS1100's, the only XS1100 that uses the same calipers as the XJ1100 are the Euro/Japanese market Sport (5K7). The Sport uses a 5/8" master cylinder for dual front rotors so this is the size to use on an XJ1100 with dual front rotors. And the good thing about that is its the most common size M/C used of other bikes..

Uh, Tom, I gotta disagree with you on this one. While the XJ uses a different design caliper, it shares the same caliper piston diameter with the XS 'standard' brakes; 38mm (and I have physically verified this). So the 'hydraulic volume' is the same as the standard XS. The XJ caliper does have slightly less pad area, but not enough to worry about.

So using a 'standard' 11/16" bore XS front master (off either model) will give you OEM 'feel'. You can downsize to a 5/8" bore, but it will increase lever travel and a few owners have had trouble at that size with stock-type hoses with the lever bottoming before full braking pressure was applied.

The Special fronts and LH/XJ rear calipers do use the larger 42mm pistons.

[BillyRok]

Mack do you have contact info for "Russell" for the SS lines? Thanks

[TomB]

Uh, Tom, I gotta disagree with you on this one. While the XJ uses a different design caliper, it shares the same caliper piston diameter with the XS 'standard' brakes; 38mm (and I have physically verified this). So the 'hydraulic volume' is the same as the standard XS. The XJ caliper does have slightly less pad area, but not enough to worry about.

Interesting stuff, I wonder then why Yamahaha decided to use 5/8" master cylinders on the bikes with dual operated rotors with this caliper, could it be that the diameter is the same as the other XS1100 pistons but the later caliper design is better causing less movement when the brake lever is released???

I have standard calipers with the 5/8" 5K7 M/C and rubber hoses, and whilst the lever movement is slightly more the brake is much more powerful. This is correct to theory too, as you get much more leverage having to use less effort but push fluid further.

I still say that the 5/8" M/C is a much better idea than the 11/16" for a powerful front dual rotor brake ....from personal experience. And think the 5/8" M/C is more suited to the later design caliper ...and Yamaha certainly thought so too

I have more 5/8" M/C's which I am refurbing to go on my other other XS1100's and my XJ1100.

Good info on the XJ1100 pistons, can't beat actual hands on experience over what I'd been informed. I also note they're a much simpler design without the step for rubber dust cover so easier to machine up in stainless.



.

[mack]

Brake stuff

I don't have much knowledge of the XJ size wise. I believe the wheel base was a bit shorter or maybe just the rake was different so the line lengths may be different for yours. What you'll need from Russell is four lines Two at 19 inches and two at 21inches. The 19's are for the rear and from the y to the front M/C. Order the 10mm fitting style.
Stainless braided #R58062s, same in Black is #R09484.
You'll need some elbows as well, rear caliper and front y (bottom) is 35degree.
Stainless #R4050c and black #R09525
You'll also need two straight banjo's, one on the rear m/c connection and one at the top of the Y. Stainless #R4047c, black is R09523
You'll also need three 15 degree banjos, one ato the front M/C and one on each of the calipers (front) Russel doesn't make 15's but the OEM number is PB 593-03c I think I got mine from goodridge but any automotive store will carry them.
You'll also need one double banjo bolt, I can't remember off hand if it was 10x 1 or 10 x 125. I'll give you the number for the 10x1.
stainless #R40507s and black was #R40508.
I always change all my banjo bolts and washers at the same time I upgrade the lines and the crush washers are purchased by the box. I'm told you can re-use them if you frreze them then dump them in boiling water for a second, or maybe vise versa. I've never bothered as they're dirt cheap anyway.
When you take off the old lines save and reinstall all the line clamps and rubber etc. You'll need them again for the ss lines.

[mack]

Just remembered

not sure if I have to mention this but you'll need three of the 35's
. I believe my cost per bike was around $275. The Russel stuff is nice to work with. You can customize all your angles with very easily with a single box end wrench.

[Rasputin]

You could also go to the site mentioned in this post
http://www.xs11.com/forum/showthread.php?t=38453
and get your stainless brake lines from the guys who run the XJ forum.
The links in the post will get you to the site for XS brake stuff, but they have lines and other brake parts available for all the XJ models. Almost every part of an XJ brake system is available through them and they sponsor that site. They also have alternate parts for modifications. JAT

[BillyRok]

Thanks for the info guys. Sounds like OEM means using a MC with 11/16" piston like the XS uses, but others have used 5/8" aftermarket MCs with good results, too. Some quick math says the bigger piston has 21% more surface area to push brake fluid...seems like a big number but maybe using SS lines help offset that? $90 for a new MC with good reviews is in the budget and patronizing our "cousins" on the XJ forum (Rasputin vouches for them) for the SS lines feels neighborly

On to the mechanics of the delink...here is a pic of the backside of the XJ rear MC and proportioning valve, an FYI for those who have never seen it.

[IMG][/IMG]

and another angle

[IMG][/IMG]

Do you recommend keeping the valve, removing the line (left side of pic) that runs to the front caliper, and plugging that hole with a bolt? What size bolt?

or

Do I remove the valve and short steel line running from the back of the MC into the back of the valve and then hook the rear brake line (resting on my ring finger in pic) into the MC where the steel line currently runs...and is that even possible?

Sorry for the fuzzy picture, my new smart phone is currently still out smarting me. Thanks.

[crazy steve]

Most have just replaced the XJ rear master with a XS unit. IIRC, some have tried modding the XJ rear, but leaving the proportioning valve in place has been an issue (I don't recall the details). You could remove the valve and go directly into the master where the steel line now connects, but the XJ rear has a larger bore so you're going the opposite direction from using a 5/8" bore on the front. Expect a short-travel, hard brake pedal with poor 'modulation'...

[petejw]

you need to remove the proportioning valve.
when its linked it allows more pressure to the
front brake than the rear.