1986 KZP forks.

Just got this bike and its clear the front is in need of stiffening up. There are schrader valves on the fork tops. Any idea how much air to put in (assuming this increases pre-load). What weight oil should I be running? 
Any after market spring s I should be looking at? 

Thanks in advance Folks, Dino

sonic springs have been mentioned here on kzr. progressive is another brand. fork oil: the 1981 chain drive pdf fsm says SAE 10W20 but check the P5 supplement. probably 10W or 15W fork oil. i'd lean towards the 15. if you change the fork seals, try to get oem. if nla, then K&L. for more of an upgrade: racetech cartridge emulators. but installing those is more involved. air. see if you can air them up evenly to about 7.5 psi. the supplement would have the correct pressure. imho. it's near impossible to do. so I don't bother. but my motorcycle is a 650. probably need a fork air pump and quality low pressure gauge.

regarding the manual: the 1981-83 fsm serves as the base manual for the 1000P police motorcycles, then you'd need the police supplement that covers the P5. ebaayy search: 1986 kz1000 police manual. a couple for cheap. under $20.