Hi,
Carried out routine filters, plugs and oil service on my '91 K75S and whilst the filter box was apart I checked the crankcase breather hose which turned out to be split. Fitted a new one and yeeeeehaaaa! Its a new bike! So, my advice is check that hose and fit a new one if needs be. Its an easy, cheap repair and the benefit is that much joy abounds.
Keep 'er lit,
Andy