To put it in perspective, if I go "hands off" I have to lean my body about 6 inches to the right to run straight.
That is what I had to do on my two unmodified Combats to run hands off, lean my mass to R some. The dozen or so Cdo's I've checked with factory laced rim were all ~3/8" L of spine/loop center. This plus the ~3/8" LH offset of the power unit would make sense it'd tend to drift/fall L rolling. The heavy cast iron drum is also on the LH side to bias some more in those.
There is scuttle butt about lightening the steering effort of 850 increased trail by mass of caliper ahead of the stem steering axis as Bob just mentioned on moment of inertia.
The iso gap wear and re-shimming to sit cockeyed in frame can be a factor as mentioned too. I don't think fork action or fluid balance has much if anything to do which way innately tends to drift as I've had a fork leg drained to rusted inside w/o noitice but for stiffer fork action rougher ride on surfaces. Also sticky stem bearing. Combined it did not change drift but boy howdy it'd magnify the slight road lumps into jerks opposite the way intended by pilot.
I've run with a bent swing arm that would not pass spindle again once removed and with lower shock mount flopping in the breeze, neither affected the basic drift but did make road undulations cause hinged handling onset at legal speeds & moderate gusts in mild turns to compensate for by easing off radius and lean.
On Trixie Combat that deer struck out from under me so cylinder struck apart L knee, so hard apparently it bent the spine under tube to L ~3/8" of spine center and to fit head stead required ~1/4 offset shimming, it still handed as fine as any 750 and drifted L hands off as prior undetected till hands off a while. This is why I'd suspect frame and power unit placement as low on list influence on drift or aim or anything else but assembly terror and some buzz through headsteady from side wind loading or harder leaning loads at mostly legal sane turning operation. Very soon I will be taking a sludge hammer to the small tube to bash it back a bit for less struggle/screaming to mount head steady, hopefully removing the buzz intervals Trix had after the deer strike rebuid, but not expecting any affect on innate drift or direction.
On my Peel I've centered rear rim to spine, 3/4 less weight RH disc rotor and removing as much mass off L and moving to it R to see if that reduces L drift and security to fling to max one side or the other. On the Cdo that do not drift L mildly I'd suspect some fault that is compensating opposite of normal.
One thing not mentioned that caused wobbles out the blue at 50-55 mph, so definitely not hands off or it increased, was slack in the main shaft sleeve bushes/clutch wobble that triplex and drive chain flop tugged on to shift rear to front tire relations, till tranny renewed. Set bike on frame tubes and tug on chains to see if it caused swing arm to front iso mount shifting in rhythm.
I've check wheels rolling in same line by inflating tires hard and rolling through wet cement then across dry to view tracks. So far could not detect anything off that way.
Maybe your solution will be a new one to us all.
