crazypj said:CB450 never used a 1 piece all iron cylinder.
Only time I've seen that was on the CA192 and similar from early 60's
There is a thread on Honda Twins about modifying 71mm Suzuki GS450 pistons to fit CB450 as I believe they are still available from Suzuki cheaper than aftermarket pistons (Henning's, et.al.)
70.11mm is roughly 0.005" oversize, not much further to get 0.25mm over pistons in there (0.010")