Just got a vintage bike 1978 Suzuki GS750 MC. Changed the front fork oil to 180cc (6.1U.S oz) and the forks seem to be bottoming out when I hit a bump. I used SAE 20. Can anyone tell me what amount of oil has worked for them?
Probably have to do a search, or find a manual. But that does sound like about the right amount. Too much and they may go bang, as in solid over a bump. Proper fork oil is always best, but I have used other oils. Any change the forks need air?
You will find a factory manual here for download (The forks were designed with air assist but will probably not hold it if you don't rebuild the front shocks. Progressive springs work nicely with no air assist.): http://members.dslextreme.com/users/bikecliff/