A good article on wheels
I installed Marchesini forged magnesium wheels on my 2001 Ducati ST4 and saved 5.46 lbs in front, 5.24 lbs out back. I also replaced the stock stainless steel rotors with ductile iron rotors, saving 3 lbs up front and 1.5 lbs out back. And I went with a 180/55 profile rear tire vs a 170/60 thereby saving some weight in the sidewalls. If I remember, the rear tire saved about 1.5 pounds and that's rotating weight far from the hub which is a very good thing.
Front OEM wheel: 11.5 lbs. Marchesini forged magnesium wheel: 6.04 lbs
Rear OEM wheel: 13 lbs. Marchesini forged magnesium wheel: 7.76 lbs
The difference was dramatic! On the first ride, in the first corner I almost ran the bike off the road on the inside of the turn. The steering was that much quicker. I rode for a few more minutes and then returned to the garage to lower the rear ride height and slow down the steering.
Over the next few days I adjusted to the light/quick steering and realized that this new "feeling" was not only dramatically differnt from the OEM wheels, it was pure pleasure and I said to myself "I want this feeling on all motorcycles I own from now on". It is that nice. In a way it's like power steering. The bike feels much lighter and much smaller. It reacts instantly to your inputs. It feels the way I would imagine a race bike feels. Very pleasureable.
Over the next few weeks I raised the rear ride height back up and that Ducati is an amazing thing to ride.
The Marchesini forged magnesium wheels were $2400 a pair, new, back in 2005 (if I remember).
Would I do it again?
Carbon fiber wheels have a better moment of inertia but the Marchesini forged magnesium wheels are a very close second. Some forged aluminum wheels have a poor MOI and I wouldn't waste my money on them. You have to do your homework.
Without knowing the weight of the stock K1600 wheels it's impossible to know how much of an effect lighter wheels would have but lighter is better as long as the MOI is improved. Lighter at the edges, the furthest from the hub is where it matters most. CF wheels are best there - forged magnesium are very close.
I see wheels have become VERY expensive since 2005 so I personally wouldn't do it again. And it is possible our K1600 stock wheels are greatly improved and lighter compared to the anchors from yesteryear.
Find out how much the stock K1600 wheels weigh and their MOI. A good article on wheels.