Royal Enfield — Missing and overflow

Address: Khatima uttrakhand ( Udham Singh Nagar)

My Royal Enfield 350 bullet (bs4) have missing problem, the service station changed the new Carburettor but the missing problem doesn’t stop and they changed 4 times but it doesn’t effect my Bullet, but now they installed bs3 Carburettor in my bs4 bike and it also goes for same problem with additional of overflow the petrol.