Z1OwnersClub GB

a bit of info needed lads and lasses,ive just measured a standard piston(903cc)its about 65.16mm.ive been offered some pistons at 67.05mm.what cc would they be for.

1mm is about 30cc

According to Wiseco

70mm is 1015

71mm is 1045

Short answer: around 950cc


Long answer:

It's the area of the bore times the swept volume



so for a standard 6.6cm bore (piston is a bit less) and standard 6.6cm stroke....



for your 6.7cm pistons its...



but that's not allowing for any piston/bore clearance so add 1 mm (not actually sure what the bore should be for your pistons) and that makes it:

so would that make them one mm overbored.

Yes.

cheers lads,it was clear as mud at first.

You'll still need to find out what the right bore is for those pistons (assuming they're not NOS with known part numbers).

Wiseco talk about bore size not piston diameter; so their 70mm/1015cc pistons are not actually 70mm wide. The 70mm is what bore the cylinders need to suit those pistons.

i understand that ruffle,my mate has lent me some barrels that are one mm overbored,so can take a measurement off them to get correct bore.cheers. i think they will be two mm overbore,and not one,as the piston i have here is one mm over,and reads 66.9 mm.

The bore needs to be the same dia as the piston and then honed to give the correct clearance . Simple.

I do recall some 'big bores' were 960. Not very popular as the engine could easily take more.

What make of piston are they?

waiting to find out what make they are.

hillbilly wrote:waiting to find out what make they are.

genuine kwak i think

cheers steve,