To de-restrict fully you need to get a kit from Three Cross Motorcycles (the importer) It costs around £300, and if you get a dealer to fit it the total is about £500. Power goes from 11bhp to about 33bhp!! Top speed will depend on rider size, but will be well over 100mph. Kit includes carb jettings, exhaust mods, new sprockets for gearing changes (fit a new chain as well) Be prepared for an engine re-build every 10,000km or so though, this will fly but puts a lot of strain on the engine. Make sure you can source those parts you may need for overhaul, piston/rings/barrel, bottom end bearings etc, before commiting to e de-restriction. Have fun!!