Air valves in fork tubes?

My 1982 KZ750 has what looks like tire-type air filler valves at the top of the fork tubes. I have not yet found these in the manual. What are they for, and what to do with them? Thanks!

you have air and oil damped forks i usally try to run between 10-20psi in mine don't use an air compresser as it fills to quickly and could cause the seals to blow i always use a small hand pump like a bicyle pump.

I could be suffering from serious memory degradation, but it seems like Kawi specified 0 - 8 psi, with 4.8 being "normal."
Your mileage may vary.

I'd go with the lower figures too. Especially if you don't know if they have been pressurized in a while. Nice to have a crossover too so both forks get equal pressure. Hand pumps are a good idea as TB said. GLuck!

Information from the KZ650-CSR factory manual.
Check the air pressure when the forks are cold & w the front wheel off the ground. Do not use a tire gauge to check the pressure (it won't be accurate for low psi). Adjust the air pressure so that the forks are within 1.4 psi of each other. The recommended front fork air pressure for the 81 650-CSR is 7-14 psi. Do not exceed 36 psi. The maximum pressure listed on the CSR forks is 35 psi. The 650-CSR weighs a little less than your 750-4.

Hmmm, could be old Concours memories leaking in here...........

On my 82 kz750, I use a hand pump and a digital air pressure gauge. I've found that I like'em at around 10 psi. I usually have to check them every couple of weeks to make sure they are even.

i tend to ride my bikes pretty hard so i do tend to add a bit more air than is normal myself but it is a very adjustable thing so make sure you ride it and try it at different settings. also it is important that you have the same in both forks unless specified or you have a cross over line like was mention i my self don't have one of those.

"Normal" fork air pressure depends on what bike you have so you really need to know the correct specs. For instance, while 7 - 14 psi might be correct for the 650/750s, recommended pressure for my 82 GPz 1100 is 25 psi.

Okay, so don't use a tire pressure guage? I don't have a digital one but could probably find one. About the crossover line; can one be handmade, or should they be purchased, and where do they attach, at the air fittings?

A digital gauge may work fine (was there such thing back in the day?)

if you get the right hand pump it will already have a gauge innstalled on it as far a crossover line if you have enough room you may be able to pick up one that is the right size from your local wrecking yard.