So, I've always had a light issue w the head studs pulling on the 67C2TR. as a side note, i think the casting quality on the alum cyls were the cause, as the spare cyl i have had the sane issue. I'm assuming this is why they later changed the G3 cyls to iron.
so after a few years, helicoils, time-serts, over drilling/tapping w longer studs. etc.
so, i decided to drill across the cyl thru the stud to pin it.
i drilled a 3.5mm hole thru at a 45 degree angle, then ran an m4 screw thru. carbon steel, ground the head down to fit between the fins.
can sort of see it in the pic.
then for almost a week, I've ridden it at least 10 miles per day thrn checking the torque . it finally settled in.
its unorthodox but it seems to have cured it.
its the front left stud and the right rear for some reasons were the worst. i think just casting and material quality , plus age as aluminum does weird things over time.