406 head gasket question

[enduro400rider]

im doin the 406 bore in my 400 and i was wondering if you use the stock size head gasket?? its only 1mm would it hurt?? thanks for the help

[cals400ex]

the stock bore and the 406 pistons both use the stock diameter head gasket. i would suggest using a thin cosmetic flexsteel headgasket if you want to raise the compression a bit.