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Blueprinted Thundersport 500 Class Legal Build

Are you racing at Thundersport, EMRA or any other class which requires you to comply with Thundersports rules, regulations and find you're down on speed? Do you find other bikes you are racing against are faster than your own? The problem with racing CB500's is that most of the engines come from commuter bikes with many seeing over 50,000 miles. This means the engine will be very worn out for racing terms and a worn engine means a loss of power. With these engines being mass-produced and not built for racing, the machine tolerances vary quite considerably, this also causes a loss of power. A refresh that is done correctly and blueprinted to our specifications will restore the power you require to be competitive within your class.

Your engine will be stripped, all components will be measured and assessed for any damage or wear, you will then be given a quote with all the required parts on and total cost. You can then choose to go either go ahead with the rebuild or if you don't want to, pay a £50 strip down fee and have your engine back. This spec is 100% Thundersport legal, there are no tuning modifications and will pass if stripped by the organisers.


  • Engine is fully stripped, all components are inspected and measured

  • Gearbox stripped and inspected for wear, CBs are renowned for jumping out of gear

  • Cylinders honed 

  • Bearings resized for minimal friction

  • All valves lapped using 3 different grits of lapping paste, finished on 600grit

  • Cam followers finished with a diamond rouge for minimal camshaft friction

  • Crankshaft micropolished

  • Valve clearances checked and re shimmed

  • Engine built to spec within 0.001mm 

  • 20% Discount on all genuine parts, usually just 5% more than cost. ( I pass all parts savings on to the customer)

  • Possibility of free delivery and collection anywhere in the UK

  • Full build sheet provided

  • 100% Thundersport legal

£500 Labour plus parts