1967 G15CSR Norton hybrid crank balncing

I'm going to disassemble my crank to clean the oil trap. It seems clean, but going to check. After flushing it thoroughly if I close some of the orifices and blow about 30 PSI air, it leaks and bubbles between the cheek and crank. Should this be sealed on reassembly? I didn't have any problems when disassembling the engine. Does It need to be rebalanced?

Thanks

Steve