Aprilia is £600 per barrel, £80 for a det ring and £50 for any welding required. They do however come back as new and are done to the same standard as the Aprilia GP bikes (done by the same guys in the factory).

Not really an option on a NSR250 barrel I guess but more like it when your barrels £3000 new.
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If I have to take the carbs off once more...