I think a 4.00 front rim is alittle on the large side! I think you mean a 3.5" for the front.
As for the rear you will want to try and find an RS250 wheel and make up a new sproket carrier/disk spaer for it unless you have the HRC kit.
However, the race kit for the NSR only uses a 3.5 and 4.5 so a 150 is more than enough really for a stock-ish '21.
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If I have to take the carbs off once more...