aah I see! Well I don't know what they should be tbh, but I know they will be different!
the excessive sparking will be a worn comm (the bit the brushes run against). their only really built to run for the life of the carbon brushes, maybe less. On a nice old low wattage Hoover motor I'd say replace the brushes, on a modern screamer 1400w Chinese motor (as even genuine dyson motors are Chinese made), I'd put a new one in. for the price, you've got another 10 years of use for £25!