the k1's also had hm 300 exhausts the 120 jets are suited better for them.so 110 jets would be ok on hm 341 exhausts (off the top of my head),i dont think that is your problem ? we need a bit more info. and yes check colour of the plugs to see where you are at now
you want to check the carb rubbers for air leaks dont discount anything like ignition timing valve timing fuel supply you need to go over what you have done already its all part of the fun init
BTW just came back from a friends garage hes had the carbs off his cbx 1000 ten times and you have to drop the engine too get at them lol he has the patience of a saint