I am often asked how big my XS650 engine will be when it is rebuilt so I thought this would be good to put on the web site, somewhere.

Std. bore, 75mm = 653cc

+0.25mm O/S = 658cc

+0.50mm O/S = 662cc

+0.75mm O/S = 667cc

+1.00mm O/S = 670cc

+5.00mm O/S = 743cc, the standard 750cc big bore kit, re-sleeving required, or Mikes XS big bore kit.

+6.00mm O/S = 762cc.

 So as you can see if an engine is bored to 75.50mm that makes it 662cc which is larger than our LAMS law here in Victoria, 660cc is the limit. Increasing the stroke of the engine will increase the capacity even further.  These capacities shown are for a standard stroke engine.

Regards

Daryl Hutcheon

Additional information if you want to work it out for yourself. You will need to know the bore and stroke of your engine, for example a stock XS650 motor has a bore of 75mm and a stroke of 74mm. Next you need the formula to work out the capacity of a cylinder multiplied by the number of cylinders.

Pi X R² X H = Volume or capacity of a cylinder and our motor has two cylinders X 2

 Radius(R) = bore/2 = 75mm/2 = 37.5mm or 3.75cm and R² = 14.0625cm

Height (H) = stroke = 74mm or 7.4cm

So (22/7)Pi X R² (3.75cm ² ) X H (stroke 7.4cm) X (number of cylinders) 2

= 3.142 X 14.0625cm X 7.4cm X 2 = 653.9cc

Convert millimetres to centimetres in the calculation to get the result in cubic centimetres