I had K70s on my bullet for a few years and loved the way they looked. They seemed to do everything that I needed them to, but there was one problem I could not get around. As Richard230 stated, but in my own words, they are Hell on the freeway rain grooves here in Washington state.
I thought I was going to die many times, (really) as they would catch into those grooves and start to wobble at speed very badly! My life flashed before my eyes (so to speak) more than once on expanded metal grate bridges too!
Being a somewhat newer rider it took me some time to definitively identify the problem.
Ultimately, when I changed out my front and rear tires to a different brand and type, all freeway squirly-ness stopped. My theory is that any of the old classic tread patterns with the lines going long ways around the tire may do the same thing, that may be just why modern tires don't have tread like that?
I wanted some kind of off road tread, so I put on some Kenda dual sport tires, K761 I think, and they do fine. Since I do enjoy dirt roads the dual sport tires have become my favorites.