How can I fix my Kenwood Chef KM30 mixer?

My Kenwood Chef mixer initially will start from the slowest speed till the maximum. When I switch off and then start again, it works. Even the 'Pulse' mode for the grinder attachment spins very fast. But when I fix the 'metal spiral beater' attachment, it is not working at all. I think the problem is the big blue capacitor that cannot store enough current to run the motor. I haven't changed any parts yet. I just adjusted the two springs; it works for a while, but then stops again. Should I replace all the capacitor, resistors and triacs? Please help.