Try larger main jets. 110 must be toooooo small
My bike had 105 from factory (K6 with 63hp).
If I remember correctly, these modifications were made 1980-83.
4-1 and OEM air filter box 115.
4-1 with KN separate filters 120-125.
I'm sure about this
836cc + ActionFours SS-1 (mild cam), ported head with larger inlet valves (34mm), . Mainjet 145 + throttle needles one step down from OEM setting (needle will lift and give more fuel at 1/4-3/4 throttle).
My first trip on Autobahn was made with a 4-1 with a too restrictive baffle and last engine setup. The 4-1 was delivered with 2 baffles, loud and nice + very silent. I did not test the silent one before the journey. On Autobahn when I needed to go faster than 120km/h I got problems when the max speed was 130km/h and the engine sounded as it should explode in any minute. Engine did not stop at idle and very warm for that.
I had to drive with no baffel at all... nice song in 160-210km/h. Mostly around 180km/h. Lots of people heard us!!
...all the way to former Jugaslavia, next over the sea from Venice. Then back home to Sweden again (total 4000km, 3000 without baffle). I had a nice ringing sound in my ears over a week after. My helmet then was not so insulated as later helmets. Jebs Clay Regazoni was nice helmet then but not so much damping soft stuff as later helmets.