Z1OwnersClub GB

Hello folks, thought I'd ask for a little extra help here as I fumble my way through a '78 KZ rebuilt project. The bike was pretty unmolested and my current plan is to rebuild as a tidy standard looking bike. My last Zed 1000 had twin front discs and I am hoping to put the same on mine, so here is my question:

As well as the discs and a twin splitter I have for the brake lines, I also picked up a ZRX master cylinder as an easy and not too modern looking replacement. Recent research makes me doubt whether it's as simple as that but I am getting a bit tied up in tables of braking ratios, options and what that means for feel and performance. Anyone tried this before? Alternatively are there options on good alternatives for a suitable twin disk master cylinder set up.

As an aside - I also hear of reboring an original master cylinder. Is this feasible, anyone tried it, know who offers a service in reboring ?

All suggestions welcome (I think !)

Hi Graham.Have done similar on my a2 project,you already have the splitter hopefully with brake switch and brake lines and rotors source a pair of z9 a4 or thou a1 or a2 calipers plus mounting brackets,the rh on is more difficult to find but with a bit a machining a lh one can be used,parts to rebuild calipers are readily sourced.i have used one of the double disc m/c,s David Silver stock for Cb 750,http://www.davidsilverspares.co.uk/CB750F2-(Single-overhead-cam)/part_126550/ the same as a lot fitted to big Kwaks as is period looking.The mc,s are also on ebay i sourced a couple from Maitland Racing at Stafford show,If you can find 5mm rotors thats ideal,but if you use a 7mm disc rotors as fitted to the single disc usa kz,s think about fitting progressive fork springs and use heavier weight fork oil as the front end unsprung weight goes way up with a pair of 7mms .If you want pointing the right direction Pm me,i may also have some thou calipers etc if you want to go that way.Cheers Paul J

You are welcome to this master cylinder ?
Never tried 100% and needs painting.
PM if you want it.

Hi Graham

the brake calipers of a Z1000A2 are behind the front fork, those of a Z1000A1 or Z900 A4 are in front.
The calipers of an A2 are not the same as those of an A1 or Z900A4.
There might allso be a difference in the diameter of the A2 caliper pistons... some have a diameter of 38mm, others have a diameter of 42 mm. It depended which ones where in stock in the factory! Measure them before ordering parts!
Any master cylinder designed for 2 calipers will do the job, it has an inside diameter of 5/8 inch which is written underneath of the master cylinder.
Good luck in your search!
Philippe

Thanks all for the information - much appreciated. I do have some calipers and discs sourced from eBay some years ago. Sounds like I’d better get some measurements done for them and sort out what I have.

Cass - cheers for the offer of a spare, I didn’t see your message before I ordered a replica so will carry on with that route

Phillipe - Not sure the ZRX m/c I have is a 5/8th size which was what started me worrying a while ago. With everyone’s input here though I have a good plan - thanks for your guidance on calipers etc

Hi Graham
you're welcome!
If you need some advice or pictures, just let me know, I'll be happy to help you sort it out.
Greetings from Belgium
Philippe

The ZRX MC is for twin disc 6 pot calipers so I would assume they are 15.8mm (5/8) minimum and would work fine. Just make sure you fit braided lines or you lose some of that extra anchor weight when the rubber hose expands.