Z1OwnersClub GB

I am told 998cc pistons from a Z1000J will fit in my Z1b. Current bores are 0.5 o/s and are goosed as are the pistons and rings! 1mm o/s pistons are no longer available (even tho' advertised by Z Power) have tried everywhere. Jeff at Z1 enterprises has got 3 pistons/ring sets but not a 4th new set (he is looking).

Question is :- if I go down the road of Z1000j pistons (which are available and cheaper than Z1/Wiseco) can anyone tell me the bore dimensions, piston skirt clearances etc for the Z1000j. My manual only covers the Z1 and Z1000a1/2. A photocopy of the spec page from the manual would be great, willingly pay copy/postage costs.

I have asked on here before about 1015cc Wiseco which everyone recommends, trouble is my machine shop is worried liners will be very thin hence don't advise this, hence the 998 pistons option which will leave a little more meat on the liners, albeit only about 12 thou more. So much conflicting advice is doing my swede in.

Watch the wrist pin hieght - I think it changed with the Js onwards

69.4mm bore size

0.043 - 0.070 clearance

Have you considered using z1000 barrels?. Cosmetically they have thinner cooling fins but if originality is not too important to you this may not matter. Z1000 barrels are readily available and quite cheap and you have a lot more choice in piston sizes e.g 1045, 1075 or just keep it standard 1015. Z1000 barrels will fit onto a z1b crankcase and rarely need any work to the crankcase mouths.
Gez

Rich, Thats gone and lobbed a spanner in the works!
Hadn't thought about wrist pin height, it was Dave Marsden that suggested the 1000j pistons so took him at his word. Aaaarrrrgh!!!!!!

Gez - I want to retain standard appearance so 1000 block is not an option for me - thanks for the reply.

Any more info on 1000j piston suitability anyone? Gotta find a solution soon 'cos springs nearly hear and I don't want to miss any riding opportunities.

Anyone done a Wiseco 1015 bore on a Z1? any problems with liner thickness/machining etc, knife edge on liners must be difficult to install pistons.

sure there is a z900 barrel pistons heads listed on ebay today in nottingham

john_roscoe, Just go for the 1015cc kit! I had my Z1A done by Debbens & they were great! I used to thrash the old girl with NO ill effects!
Many 100's of 903cc motors have been bored out to 1015cc without any problems!

DON'T use the 'J' pistons in a std early Z motor coz the gudgeon pin is located lower in the piston to compensate for the J's shorter conrods. You will smash the hell out of the valves etc unless you fit a barrel spacer to compensate, which is a no no if you really want to keep the bike std looking, although it would not be that noticable to the untrained eye. P.S. Only an anorak would notice any difference in cooling fin thickness so i would go in that direction or bore your 9 block to 1015 as i have done this with no probs, just got to be a bit more carefull getting the rings in the bores.

I am running Z1000j pistons in my Z1B with 903 block, when I got the bike they where allready installed and didnt know what was in there until I stripped the bike for a rebuild. A standard base gasket was fitted and the only problem I had was pinking on low grade fuel, when I rebuilt the engine I use a cnc spacer from Debbens to lower the compression ration and everythings fine. Still get like pinking on crap supermarket fuel tho.

You do need a 40 thou base gasket to adjust the deck height. More than that, the domed crown of the piston is shaped differently - bear in mind the combustion chamber of the J head is shaped for a 69.5mm bore - so there is a likelyhood the J pistons would come into contact with the head unless you switch to a J head - so clearly not worth it.

The Wiseco kit is a good option - the negative is the increased compression - this causes the engine to run hotter and will require higher octane fuel. You will also need to rejet slightly.

If we cannot find you the 2nd over parts, using z1000 stock 70mm pistons is an option - this retains the same basic compression as the 900. If you can pickup a nice set of used pistons, we do have 70mm rings for the engine - fairly inexpensive at about $84 (45 quid) the set.

Big thanks to everyone, will see if Jeff can get the 4th piston/ I may have found one in UK. Prefer to keep motor standard, with all the issues its had since I bought it last October I don't want any more potential problems to arise.
Failing that, I will go the Wiseco 1015 route as everyone suggests is good (great price thro Jeff @ Z1 Enterprises), as this retains standard external appearance albeit with some carb/fuel changes to suit.

Thanks again, I promise never to mention pistons/wiseco etc ever again- I have learn't loads in the process and appreciate everyone taking time to provide help/comments.

John, look at this eBay item mate: 120093433886