Z1OwnersClub GB

Hi All
Just got the top end apart on 1976 z1000a1.

Pistons seem reasonable condition - they have ART stamped - Also direction arrow,
external diameter - is 69.70mm below the rings. Varies slightly up the length by +/- 0.30mm

I am presuming these are Kawas originals?

If so, is there a way of determining a mileage from the sizes?
The clocks have 25K on but I'm presuming that's random.

Thanks David

Those are stock thou pistons.
They taper inwards from the skirt toward the top so will measure less at the crown.
25k may be correct and if so there should be plenty of miles left in the stock pistons.
If the piston to bore clearance is within spec a hone and new rings will freshen it up.

[quote="zed1015"]Those are stock thou pistons.
They taper inwards from the skirt toward the top so will measure less at the crown.
25k may be correct and if so there should be plenty of miles left in the stock pistons.
If the piston to bore clearance is within spec a hone and new rings will freshen it up.[/quote]

Thanks for the advice.
OK will check the ring gaps and also piston clearance in bore.
The bore seem smooth all round and also at the top, no ridges to speak of - perhaps a very slight change as you run your finger over the surface - but nothing much.