Amazingly we compared the front forks and yoke from an old motorcycle with one of the latest 1000cc Japanese models you can buy in Thailand. The old forks weigh together 7.54 kilograms while the new weigh 7.58 kilograms. The yoke of the old motorcycle weighs 1.388kg and the yoke from the new motorcycle comes at 1.454kg.
Amazingly, the old motorcycle's forks have the same diameter stanchions as 1985 – 41mm. Of course, the new ones are upside-down, which gives a stiffer unit at the expense of some mass.
Having said that, the 150grams total difference is probably as much to do with the radial brake caliper mounts. New forks have more adjustment than before – separate high- and low-speed compression damping, rebound damping and preload adjustment. The old front forks have preload adjustment, and a then-fashionable anti-dive system (the gold cylinders on front of the bottom of the forks). This system altered the damping when braking, in an attempt to reduce fork dive.
The bottom yokes are worth comparing – the new part has a dual-bolt clamp instead of the old motorcycle's single bolt, making it much stiffer. The bearings are also different – ball bearings instead of the modern taper rollers. So not always think that the latest motorcycle is made with the lightest parts...