had or have this condition on my 71 500 which has changed in degree of severity from the time first got it on the road last year to this day.
first off your tyre is not stock at 100/90/19 should be 90/90/19 front which is closer to stock.
in my case, the tyre was not mounted/seated correctly which larger tyres cause from pinching in on the stock thin rims.
this was corrected by the shop that mounted it, this helped for have the 100/90/19 myself which feel is too big for the rim.
next replaced the rear swingarm bushings with bronze style and checked the true of the rims front and rear, which found to be quite out which helped as well.
have replaced rear shocks with new Ikons on the rear and rebuilt the front end. increased fork spring tension and rebuilt front forks, played with fork oil height ect, this helped tremendously as well.
for me still have a slight head wobble at around 40km but disapperars at higher speeds, which think is due to old rims that won't true perfectly anymore.
Will change out the stock headstock bearings for tapered and change the front tyre to a 90/90/19 this winter . Would like to get new rims as well, money and time...
My point being all the parts are connected in subtle ways, each having effect on one another and seemingly not one thing fixes the handling woes of a 40 year old bike.
It all could be very simple and just be a badly seated tyre or warped rims, but found with mine it's just age of the machine. Going through and replacing worn parts and correcting flaws is slowly making it a well handling motorcycle.
