The 900 is a heavy bike... Probably best not to ride without air. It is not the quality of your comfort you need be concerned with, but rather the traction you will lose with poor suspension.
With regards to Progressive Fork Springs, they are worth every penny, IMO. I would recommend replacing the Rear Shock Absorbers at the same time, as they work hand-in-hand, and most folks who do one at a time, report that the new suspension really demonstrates the failings of the old... Best to do them all at once.
I replaced the full suspension on both of my bikes, and the transformation on the Honda was amazing -- it modernized the handling of the bike by 20+ years. The improvement on the Kawasaki was much more subdued, but still worth it -- I hate air suspension, as it always seems to lose air; adding 7-9 PSI is a pain, for me, due to the low pressure, and how much you lose every time you attach the low pressure gauge to measure it... With Progressive Shocks, you just set it, and forget it. Maybe not as adjustable, or plush, as air, but the lower maintenance is worth it, in my book. Cheers!
1979 CB750K (sold, 2012, but not forgotten)
1983 Kawasaki 440 LTD Belt Drive (sold, 2011)
1993 Kawasaki Voyager XII
Locked
