This may, or may not help.

MC21 HRC ign timing #1/2 cylinder 23deg @ 6,000rpm
#1/2 cylinder 14.5deg @ 10,000rpm

NF5 HRC ign timing #1/2 cylinder 23.5deg @ 6,000rpm
#1/2 cylinder 15.5deg @ 10,000rpm
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If I have to take the carbs off once more...