My late, lamented, 1982 (?) DOHC CB750-F Honda came with air forks, as was trendy at the time. My KZ1300, of course, has both air forks and air shocks. Inflating these with an air compressor is potentially disastrous, and bicycle pumps these days also are capable of delivering far too much pressure.
Back in the day, I bought an air fork inflation tool from my Friendly Dealer that was nothing more than a big medical syringe with a short inflation hose grafted onto it. I also bought a low-pressure stick-type air gauge. Together, they did an adequate job. When I sold the bike to a friend of mine, I threw in the inflator, so am back looking for an alternative.
That was exactly my concern. All the various bike pumps I found online had gauges that went up to 200 psi or so, which is crazy for this application. When I had the syringe inflator, I got a low-pressure stick-type gauge to use with it, but I've never been that impressed with that technology, and in any case i gave it to my buddy (decades ago).
Here's a goofy idea: how about a dry fuel-pressure gauge? All mechanical pressure gauges seem to use the same fitting size, would a gauge made for liquid work for gas pressures? From what little I know about gauge technology, it seems like it would work, but a small internal volume is critical for the small volumes of air forks and shocks, so maybe not so good in reality.
Hi... can't advise you on a good pump... I need on myself.... but, if you're at home... and have an accurate, low psi gauge...and your usual portable air tank...then guage the air tank pressure to what you want and apply to the forks....it doesn't matter if it comes out of a 50gal air tank into a thimble.... it's still 5, 7, 10 psi.... whatever you choose... that's the way I filled mine for years and hoped it lasted the trip...
Me - bicycle tire inflator and a common digital pressure gauge. There is a safe range for front and rear shocks, so inflating and checking where it's at will be very safe. I pump it up, check, and see by how much the pressure decreases when attaching the gauge, and how much up it goes with how many 'pumps'. Then use a pick to decrease a bit, 'by ear', or pump up to the desired level, check and remove the gauge. I think 1 psi or even 2 will not make a difference.