dual disk conv. caliper placement???

one more question i forgot to ask ,,,okay two more questions...i read that the reason the l.t.d 900s came out with rear of the fork calipers was becuase testing showed dual disks mounted on the outer front of the fork created interesting handling challenges...
Can i just mount mine on the front anyway does it really make it squirely??? or do i need to swap my forks legs in the trees and spin em around so the calipers will be behind the fork????
my second dilema is the master cylinder...i have a square later model dual disk master..but... my kz900s is soooo clean and has a chromed cap to boot...must i switch to the other master..crazy question now...can i bore the kz900s passage,,or do anything to adapt it to dual capacity..thanks for any help...peace craig

just use the proper master or go get one from a late model dual disc cruiser their all shiny and blingey stock the main thing is use a master set-up for dual disc it's much safer in the long run.i would also do the spineroonie thing with the fork tubes as well just think how much shorter the nice steel braided hose will be and also easier to route than front mounted calipers.

o.k i agree..just sometimes you can't believe everything you read...peace

trianglelaguna wrote:

... read that the reason the l.t.d 900s came out with rear of the fork calipers was becuase testing showed dual disks mounted on the outer front of the fork created interesting handling challenges...
Can i just mount mine on the front anyway does it really make it squirely??? or do i need to swap my forks legs in the trees and spin em around so the calipers will be behind the fork????
my second dilema is the master cylinder...i have a square later model dual disk master..but... my kz900s is soooo clean and has a chromed cap to boot...must i switch to the other master..crazy question now...can i bore the kz900s passage,,or do anything to adapt it to dual capacity..thanks for any help...peace craig

Am pretty sure dual calipers on front sides of forks do NOT impair handling (more on this below).

I recall a post by steell in an earlier thread informing us that somebody out there does indeed bore out the 14mm m/c to 5/8" , however I don't know much about that, or the cost involved, so am not in position to offer an opinion.

The chrome cap on hand may fit a 5/8" barrel m/c from 1976 KZ900-B1 LTD, provided a good used LTD m/c could be obtained (and restored). But that's likely to involve more trouble and expense than it's worth.

And imo it is a really bad idea to fit a 14mm m/c with dual front discs. (Could do a search for lots of info already existing about that subject, and some differing opinions and experiences).

1973-1976 KZ900 used the 14mm "barrel" m/c and single front disc.
1976 KZ900-B1 LTD used a 5/8" "barrel" m/c and dual front discs.
1977 KZ1000 continued the 14mm "barrel" m/c and single front disc.
1978 KZ1000 used a 14mm trapezoid m/c and single front disc.
1979 KZ1000 used a 5/8" trapezoid m/c and dual front discs.

Here is some detailed information from the Z1 development history as supplied by Dave Marsden, who is a well-known Z1 historian, author, and widely recognized expert and authority in the field.

Forgive the all-caps as used in the original text.


Beginning with the 1973 Z1:

THE SINGLE DISK SET-UP WAS DESCRIBED BY KAWASAKI AS "RETRO ROCKET." HOWEVER, MOST OWNERS WERE LESS THAN IMPRESSED. THE RIGHT HAND DOUBLE DISK CONVERSION KIT THAT KAWASAKI OFFERED AS AN OPTIONAL EXTRA WAS EXPENSIVE BUT ESSENTIAL. THE COST WAS MORE THAN 10% OF THE TOTAL MOTORCYCLE PURCHASE PRICE. THE PART NUMBER FOR THIS KIT WAS 99990-523. THE KIT CONSISTED OF ANOTHER DISK, EXACTLY THE SAME AS THE LEFT HAND ONE ALREADY FITTED, A RIGHT HAND CALLIPER, A MASTER CYLINDER WITH A BIGGER PISTON, ANOTHER FLEXIBLE BRAKE HOSE, A RIGHT HAND METAL BRAKE PIPE AND ANOTHER BRACKET TO SANDWICH BETWEEN THE FENDER AND THE RIGHT HAND FORK LEG TO HOLD THE NEW BRAKE PIPE. ALSO INCLUDED WAS A FOUR-WAY JUNCTION BOX, ALL THE RELEVANT FITTINGS AND AN INSTRUCTION MANUAL.

MANY RECENT OWNERS HAVE FOUND IT VERY DIFFICULT TO OBTAIN THE GENUINE KIT AND HAVE RESORTED TO USING A LEFT HAND CALLIPER WHICH CAN BE TURNED AROUND AND MADE TO FIT. A "DOUBLE DISK" MASTER CYLINDER IS ALSO VERY HARD TO OBTAIN, RESULTING IN PARTS FROM MUCH LATER MODELS TO BE USED.

ALL "DOUBLE DISK" CYLINDERS HAVE "5/8" STAMPED ON THEM ON THE UNDERNEATH. THIS REPRESENTS THE SIZE OF THE PISTON. SINGLE DISK SIZE IS HALF AN INCH.

[Some very minor changes were made in 1974 and 1975, but believed not relevant here.]


Enter the 1976 KZ900:

FRONT WHEEL:

THE FRONT HUB OF THE Z900-A4 WAS CHANGED FOR THE ONE THAT WAS ALSO USED ON THE 1976 KH250-B1 AND THE Z750-B1 TWIN. THIS HUB WAS NOW FINISHED IN A NATURAL SILVER FINISH AND NOW ONLY USED FOUR 10MM BOLTS TO HOLD ON THE DISK PLATES INSTEAD OF THE PREVIOUS SIX.

THE AMERICAN MODEL WAS STILL ONLY FITTED WITH ONE DISC, SO A CHROME BLANKING PLATE WAS ATTACHED ONTO THE RIGHT HAND SIDE OF THE HUB BY TWO 5MM ZINC PLATED PAN HEAD SCREWS.

THE SPEEDOMETER GEARBOX WAS NOW A SEPARATE ITEM AND WAS FINISHED IN AN ALLOY SILVER COLOUR, AND NOW DOUBLED AS A SPACER FOR THE LEFT HAND SIDE OF THE HUB.

THE FRONT AXLE ITSELF WAS MODIFIED TO ACCEPT TWO LARGE NUTS, WHICH SCREWED ONTO THE AXLE, ONE ON EACH SIDE. A MODIFIED SPACER WAS ALSO USED ON THE RIGHT HAND SIDE OF THE HUB.

THE HUB WAS SMALLER THAN THE ONE USED ON THE Z1 AND SO REQUIRED DIFFERENT ANGLED SPOKES AND CONSEQUENTLY A DIFFERENT RIM. THIS RIM STILL REMAINED A CHROMED 19 INCH ITEM FROM THE TAKISAGO COMPANY.

FRONT BRAKE ASSEMBLY:

PERHAPS THE BIGGEST IMPROVEMENT ON THE A4 WAS IN THE BRAKING DEPARTMENT. MOST MODELS WERE NOW FITTED WITH TWO DISKS AS STANDARD INSTEAD OF THE PREVIOUS ONE.

THE AMERICAN MODEL, HOWEVER, WAS STILL ONLY FITTED WITH ONE AS STANDARD. HOWEVER AN OPTIONAL TWIN SET UP WAS OFFERED AS A GENUINE PART FROM DEALERS.

THE DISK WERE NOW BOLTED TO THE FRONT WHEEL HUB BY FOUR ZINC PLATED 10MM BOLTS AND SECURED WITH TWO TAB WASHERS. A CHROME THIN PLATE WAS UTILISED ON EACH SIDE OF THE HUB TO SMARTEN UP THE ASSEMBLY.

THE DISKS ON THE TWIN SET UP WERE TWO THIN 4.5MM THICK ITEMS WHICH HELPED TO REDUCE UN-SPRUNG WEIGHT, WHILE THE SINGLE SET UP USED ONE 6MM THICK ITEM.

THE CALLIPERS WERE A NEW DESIGN THAT WAS BEING USED ON ALL 1976 ROAD BIKES. THE BODIES OF THE CALLIPERS WERE NOW A ONE PIECE UNIT WHICH USED TWO 10MM HEXAGON BOLTS INSTEAD OF ALLEN BOLTS TO HOLD THE SLIDING PAD HOLDER. THE USUAL ARRANGEMENT OF RUBBERS AND O`RINGS WAS USED BUT THE PADS THEMSELVES WERE OF A DIFFERENT DESIGN AND OF AN IMPROVED MATERIAL.

THE BRAKE JUNCTION BOX NOW HAD AN EXTRA OUTLET ON IT, TO WHICH THE SECOND FLEXIBLE HOSE ATTACHED TO. THIS HOSE RAN DOWN TO ANOTHER SHAPED METAL PIPE AND ATTACHED DIRECTLY TO THE SECOND CALLIPER. A CHROME BRACKET WAS SANDWICHED BETWEEN THE FENDER AND THE RIGHT HAND FORK LOWER TO HOLD THIS HOSE IN PLACE.

THE MASTER CYLINDER WAS FITTED WITH A LARGER PISTON ASSEMBLY, SO THAT IT COULD COPE WITH THE EXTRA FLUID REQUIRED FOR THE SECOND CALLIPER. THE CYLINDER WAS STAMPED UNDERNEATH WITH THE LEGEND "5/8" WHICH WAS THE BORE SIZE OF THE CHAMBER.

THIS SECOND BRAKE TRANSFORMED THE A4 INTO A FAR BETTER MOTORCYCLE THAN THE Z1 AND BECAME THE INDUSTRY STANDARD ON ALL JAPANESE MOTORCYCLES.

SO WHY DID THE AMERICAN MODEL ONLY GET ONE DISK ?. PERHAPS THE LOWER SPEED LIMITS IN THE STATES MEANT THAT THE RIDERS OVER THERE DID NOT GO FAST ENOUGH TO WARRANT THE EXTRA BRAKING POWER. !!.
OR PERHAPS KAWASAKI JUST WANTED TO EXTRACT A FEW MORE DOLLARS FROM THEM FOR THE OPTIONAL SECOND BRAKE KIT. !!


Enter the LTD 1976 KZ900-B1:

THE FORK LEG BOTTOMS WERE REVERSED SO THAT THE CALLIPERS COULD BE MOUNTED ONTO THE REAR OF THEM. THIS WAS BELIEVED TO IMPROVE WET WEATHER BRAKING.

FRONT BRAKE:
TWO DISK BRAKES WERE NOW FITTED AS STANDARD AND BECAUSE OF THIS, A LARGER CAPACITY MASTER CYLINDER WAS REQUIRED.

THE TWO METAL BRAKE PIPES CONNECTING TO THE CALLIPERS NOW HAD TO BE SHORTER BECAUSE OF THE NEW BRAKE SET UP.

A LONGER SPEEDO CABLE WAS ALSO NEEDED TO ROUTE AROUND THE LEFT HAND CALLIPER BODY.

---

Good Luck with however decide to proceed!

On my 75 Z1B, i had the MC bored by a machine shop to the 5/8 size.
Pretty easy since the shop manual give the correct bore size.
it was then just a matter of using the 5/8 MC rebuilt kit.

That said, the lever was way too hard for my liking and i have since then used the "regular" 14mm single disk MC on my dual disked Z1
I really like it, it feel like power brake with very good feel and control.

I still have the 5/8 MC in very good shape if intersted.

Luc 75 Z1B

wow folks,
you are great...all the answers are sensible and like timebomb said ...i think i should give it a try the way sugggested by the reading i had done. and be sure i'm not gonna get a lesson down the line..
that said
patton you are great ,that info is really cool and i need more time to re-read it..girl just got home...
and luc your info is reassuring cause i might run my m/c for the first trials. what a great website, i've wanted to build one of these proper for twenty years and now with everyones help i'm doing it ..thanks peace craig..

hey buddy whatever you decide is cool it's your bike just be safe and if something doesn't feel right it probably isn't .

yes i agree,the first thing is getting everything together and getting time to work on it..i spent all day sat and sun .i start spinning in circles and polishing parts...you know how it is..then i see something and work on that...ha,ha good problems to have...zen and the work shop..peace craig..probably just gonna do it the way it is suggested..timebombs theory is safe

Moving the calipers to the rear of the forks lowers the calipers mass/weight to have less "influence" on the front end when turning.
With the caliper mounted to the front of the forks, the mass/weight is higher and will have more "pull"(leverage) when in a turn(tends to "fall" to the inside of the corner). Moving the calipers to the rear of the forks lowers the mass/weight and lessens its influence (leverage) to "fall" to the inside of a corner.

IIRC, it's called "Polar Moment of Inertia", all the tech writers for the magazines covered it back when these bikes were new.

Im doing the double disk swap up front and single in the rear on kawi mags on my 74 z1. Im going to mount the callipers on the back of the forks also. Plus all the new sport bikes, such as the zx-14, busa, gsxr and such all have them mounted on the rear of the forks, must be a good reason huh??