Suzuki 2 Strokes

Guys, I have a 1975 TS400 in real good condition. On small sharp bumps something is loose in the front end other typical street riding I don't feel it. I originally thought my steering head was loose so I checked, replaced the bearings and re- tightened, but still kind of loose. So now I'm thinking its the forks. The bike has very low mileage so I don't think the fork bushings are worn out if it even has any. So I'm just going to replace the fork oil and see if it helps. Any recommendation on oil viscosity and amount?

I repacked the steering bearings and tighten everything snug properly. I took the forks apart and no apparent wear. I replaced the old oil with new and still something "clunks" in the front end. I thought it could be my forks topping out, but forks seem fine. Anyone out there seen this issue? Any suggestion?

check the fork spring length ,i know mine were on the low side which gave me them same clunk.
if you want a quick fix you can cut a short length of pvc pipe to take up the slack.