Hello!

Upgrading your MC16 to a MC21 is going to be rather tricky. The MC16 and '21 are two very different NSR's.

If you want more power from your '16 search the forum as it has been covered before but the basics are..

MC18/21 top end
MC18/21 carbs
MC18 Mk1 electrics if you must (the MC16 set up though isnt all that bad).

I'm afraid CBR600 vs NSR MC16 fight will go in favour of the CBR 90% of the time.
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If I have to take the carbs off once more...