Power wise in anything like stock or easily modified form drunkenb might have a point, though Honda did reckon gearing changes and better mid range meant the stock '28 was no slower despite being missing 5 bhp.
Handing though isn't as good and unless you swap that rear wheel for one from a '21 and do something with the suspension you can't get really good tyres.
Wayne once said (back when '18s were very cheap) the best way to spend £500 and go faster if you had a '28 was to buy an '18, conversely I'd say the best few hundred quid you could spend on an '18 would be a '21 frame, swingarm and rear wheel. The rest of the bits you can probably buy/sell or swap.
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Please do not PM me technical questions, if you can't find it on the Forum start a thread