Grab your front brake (you have one, right?) tight and rock the bike back and forth to check for loose headset play. Turn the bars 90 degrees and rock the bike fore and aft also. If you detect any play your headset needs adjusting. Adjust it.
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1989 Schwinn Paramount OS
1980 Mclean/Silk Hope Sport Touring
1983 Bianchi pista
1976 Fuji Feather track
1979 raleigh track
"I've consulted my sources and I'm pretty sure your derailleur does not exist"