Try our new info resource - "Aladdin's Cave" (Main menu)Just added a separate link to Ash's Dropbox thread (shortcut)
It is rare for a 500 to need a rebore John but, if it does need, use these >>http://www.ebay.co.uk/itm/HONDA-CB500K-CB500F-0-5mm-56-5mm-Oversize-Pistons-Set-4-Pistons-included-CB500PS-/252159005869?hash=item3ab5d914ad:m:mVeOMf_ufOFE836bq389_kw