Z1R - Piston markings and bore measurement

Hi guys,
Am pulling down a Z1R motor (D1) and the pistons have the following markings in the top - 022P XA.
Can anyone tell me what these mean please?
Also, Am trying to work out whether a rebore is required or just a hone and new rings - any guidance on how to measure bore and pistons would be greatly appreciated - I'm struggling to find details of original bore (think this is 70mm) and standard oversizes to work out if I need standard pistons or a big bore kit (would rather not go down this path if possible).
Thanks in advance!
Cheers,
Ian.

Now I've cleaned some more I think there's a 4 in front so it is 4022PS or 4022P5 then XA underneath.
These are stamped dots.
There's also 400 in raised characters on the underside of the pin boss.
Cheers Ian.

Hi Ian - mate those are Wiseco pistons, stock bore size (70mm).

Stock bore size is 70mm, the piston needs to be measured at 3 points, 90deg apart, in order to determine whether it is still in spec or not. Same thing with the cylinder bore. Normally you want the piston/bore clearance somewhere in the range of 2 thou to 3 thou (0.05 to 0.07mm). You also need to spec the ring gap, normally measured at 3-4 thou per inch of bore. 70mm = 2.76 " , so you want around 10-11 thou clearance for the top ring and slightly larger for the 2nd ring - 12-15 thou.

If the pistons are still a good snug fit in the bores - at TDC, middle of stroke and BDC - and the barrels are not scored or have a big ridge around the very top edge - I would think you can just get some new Wiseco XA rings, give the bore a slight hone - and re-fit those pistons with new circlips. The original gudgeon pins - unless really heavily blued or scored - will be fine. The only issue you might have, is whether Wiseco still make XA-style rings. They did use different styles of rings in Kawasaki z900/z1000 motors over the years.

If the clearances are too big - you may need to go to 70.5mm or even 71mm (1045cc) pistons. These are still available through Wiseco.

Hope that helps

Thanks Gos - you are the man!
Good to know it is still on standard bore as suspect will need a rebore as there is some scoring in some of the bores.
Any suggestions on source for new pistons/rings appreciated.
Another interesting thing is that #3 piston had a different oil ring to the rest - does make me wonder about the history...
I will add pictures when I can work out how this is done!!!
Starter motor bolts were broken off flush with the casing - have attempted to remove - unsuccessfully - so guess I'm looking at re-drilling and re=tapping or helicoil.
Cam chain guide was in the sump - the other bits of it were still in situ.
This project is an adventure!!

hmmm - that is some serious scoring. At a guess I would reckon 1mm o/s pistons would sort that out - but you need to take the barrels in to a bike specialist and get them to run the micrometer over the bore to confirm - remembering that 1mm o/s is only 0.5mm all the way around - if those score marks are deeper than half a mm - then you may need to go bigger again.

Wiseco do plenty of piston kits, so do JP pistons. All sourced from the US, you can buy Wiseco stuff from the aussie distributor (Serco) - but I generally just go straight to the US for parts......

I couldn't tell from the photo of the rings, what the difference with the #3 oil rings was ? One thing with the #3 piston & rings - they tend to wear out sooner than the others, because the #3 crank-web has the primary drive cut into it, directly under the #3 piston......this means a shitload more oil-fling in the #3 piston - and more work for the rings from below as well as above. #3 piston is generally the first piston to fail in old z motors.

Having parts of the CCT floating about in the sump - is normal - Most times it will be the front tensioner, which is only a small piece that tensions the front lower run of the cam chain. These normally fracture at the 90-deg bend where the tensioner bolts into the barrel - the longer front section then just drops into the sump - sometimes in one piece - sometimes in more than one piece

I would take the upper case into a thread specialist and get them to remove the busted bolts electrically, this does the least amount of damage to the threads in the cases. Important to have these working properly - unless you like kick-starting your bike (and on these old rigs - its a pretty cool thing to be able to do )