soft brakes twin disc set up

"Just guessing, but perhaps the horror stories are in part due to onset of a severe emergency braking situation before the rider grew accustomed to the more sensitive front braking."

That will make perfect sense.

PLUMMEN wrote:

The problem with locking up the rear wheel is all the weight is being shifted forward as you stop ,taking weight off off rear wheel and sticking it over the front wheel.

Thats the reason for those big rotors on the front and small ones on the rear ,just like on a car/truck.

I can dig it ,especially on a FWD car. Ive never had a bike swap ends with the rear brake firmly applied. However,I have had dirty skivvies a time or two when I instinctively grabbed a handfull of front brake in a near miss situation.Then the bike wanted to swap ends and my end was clutching vinyl.Oh well,to each his own driving style.Be safe all.bj

hocbj23 wrote:

I guess Im just not proficient enough,but the first lever I reach for in a hard stop is the clutch--so I can shift down and use engine compression for a quick slow-down or stop.Locking up the rear tire with its larger contact patch seems a lot safer than locking up a front tire and losing all steering control.I seldom use my front brake and that only for holding the bike at a traffic lite.I been riding that way for a long-g-g time and no issues yet.I guess if bikes were FWD and being pulled instead of pushed I would feel differently.bj

And you are still alive to post here? Amazing!!

Dude, use your front brake and stay alive!!
Seriously.

The only time I use the rear brake on my 750 twin is when I'm already at a stop and use it to keep the bike from rolling.

I don't know if I could lock the front tire with just one finger, but I know I could with two.

Mix and match brake components:

96 GPz1100 master cylinder (15mm I think)
Dual braided stainless lines between master cylinder and calipers. Got rid of that brake splitter.

83 GPz750 calipers.

80 KZ1000 brake disks

on a 79 KZ750 twin.

I love it!! Best brakes I've ever had on a bike! I can easily out stop the 85 GPz750 Turbo and the 82 KZ1000.

GPz750 has 10" brake rotors, the 1980 KZ1000 has 12" brake rotors. That's 20% more radius which equals 20% more stopping power using the same calipers.
I think the GPz750 had a 5/8" master cylinder but I'm not sure. If true then that would account for even more stopping power with the 15mm.

Been two years so far and no problems yet.

I think I could do a stoppie, but I lack the intestinal fortitude to attempt it. :blush:

dam10r wrote:

So if I keep the stock MC what is the best way to bleed the lines? I have done it many times, but can't get rid of the sponge. Thanks for all the other suggestions!

Buy yourself a Mighty Vac as a previous poster said. Start bleeding from the furthest caliper from the MC. Tap the lines with a screwdriver handle as you go. Quick movements of the brake lever expell small bubbles in the MC. A nice set up are the braided SS brake lines where each line goes up to the MC. Get rid of the splitter. Hope this helps.

I know this might be resurrecting a dead thread, but steell how did you eliminate the splitter running a dual disc set up on the '96 GPZ1100 Master Cyl.? There is only one outlet from the M.C. and obviously needs two lines (one to each caliper). Am I missing something here? :huh: Seeing as I have your old GPZ M.C. and two discs on your old set of mags (Thank you-they fit great! pics soon to come), this is of great interest.

Buckeye73z1 wrote:

...how did you eliminate the splitter running a dual disc set up on the '96 GPZ1100 Master Cyl.? There is only one outlet from the M.C. and obviously needs two lines (one to each caliper). Am I missing something here?....

Perhaps a double banjo bolt at master cylinder.

Click > www.z1enterprises.com/SearchResult.aspx?All=True&KeyWords=banjo

Good Fortune!

Some riders have has success by having the front brake lever squeezed overnight by use of a ty-wrap or rope. This lets most of the air bubbles out of the system.

Make sure there's enough brake fluid in the reservoir before calling it a night. Install the brake fluid cover after checking, put a ty-wrap squeezing the lever closed and check the next day.

MFolks wrote:

Some riders have has success by having the front brake lever squeezed overnight by use of a ty-wrap or rope. This lets most of the air bubbles out of the system.

Make sure there's enough brake fluid in the reservoir before calling it a night. Install the brake fluid cover after checking, put a ty-wrap squeezing the lever closed and check the next day.

We used to do that at the roadraces, after coming off the track from a race or practice session. It just takes light pressure on the lever to open the fluid circuit. Good tip.

Wonder if the OP ever sorted the problem?

By the way, if anyone has a Z1/KZ900 style rotor and right caliper (or even just a right caliper bracket will help)I am interested in buying it. I still have my Z1 forks and this limits my caliper choices. I was going to swap out my forks for Later KZ1000 forks and go with the newer calipers, but I've opted to rebuild my old Z1 caliper instead and need a 2nd one. I have a newer (either KZ1000 or GPZ750, not 100% certain-but I think they interchange)caliper and two KZ1000 discs I'll trade even-up if anyone is interested. I'll also sell the KZ1000 brake parts outright and am willing to buy the Z1 brake set up outright if need be. PM me. Thanks!

mjg15 wrote:

You mention that you have the original M/C. If you mean the one that was intended for a single disc then that is likely to be your problem. You will need an M/C with a larger piston to move enough fluid for the two calipers that you now have.

I'm not sure about the exact sizes on a 1000, but on the 550's that I'm familiar with the single disc bikes use a 14mm M/C and the dual-disc bikes use a 16mm unit. I would expect that you would find a similar difference on the larger bikes also. The correct M/C combined with some braided steel lines will give you the results that you were expecting.

I have the same situation on my KZ1000 LTD. The bike was equipped from the factory with dual discs. The PO crashed and wiped out the 5/8" bore MC and replaced it with a 14mm unit.
I discovered this when I bought a rebuild kit for the MC. The kit didn't fit. I got a 14mm kit and rebuilt the cylinder. I rode with that for 2 years and suffered a soft front brake. I could squeeze the handle all the way to the grip. I had reasonably good braking but not max effort and not overly sensitive. Last spring I searched for a 5/8" bore MC and came up empty. I wound up modifying the 14mm MC and installing a brass liner. It works great. I can't squeeze the handle all the way to the grip anymore. I have good control and the brass liner won't pit like the steel MC bore did.

I still have the special tools I made for the conversion and some of the brass for the liner. I'd be happy to convert yours if you like for the cost of parts and shipping. PM me if interested.

A tiny bit of air can give you fits. I bleed brakes by pumping fluid up from the caliper into the MC. It seems to dispel air faster than pushing bubbles down the hose with the MC.

Patton wrote:

Buckeye73z1 wrote:

...how did you eliminate the splitter running a dual disc set up on the '96 GPZ1100 Master Cyl.? There is only one outlet from the M.C. and obviously needs two lines (one to each caliper). Am I missing something here?....

Perhaps a double banjo bolt at master cylinder.

Click > www.z1enterprises.com/SearchResult.aspx?All=True&KeyWords=banjo

Good Fortune!

You're good!!