for anyone else who has this problem this is from hks europe
for part number 2103-rn025 87mm hks pistons
From:
m.yumeda@hkseurope.com
To:
martinloz80@hotmail.com
Subject: RE: hks 87mm pistons
Date: Fri, 28 Sep 2007 14:12:58 +0100
Ok, here’s the information you need.
On the underside of the piston, you should find 2 numbers. This demotes the diameter of the piston at 20°C for example, 75 means that the piston is 86.975 mm diameter, 80 would mean 86.980 etc.
This is measured 10mm above the piston skirt.
The piston to bore clearance is set at 0.020~0.030mm This should determine the size of your hone.
Hope that helps.
Best regards,
Masaya Yumeda
HKS Europe Ltd.