Honda XL Italia

My cylinder barrel has recently been rebored to fit a NOS oversized Honda piston (0.50)

The piston (without rings) seems very loose in the bore.

Does anyone know the exact diameter it should be so that I can check it?

Thanks

PS

someone on the German forum suggested this......

'Try the repair manual from our italian friends: "WHB_Honda_XR_Kapitel07 piston cylinder.pdf" ?????