Joined: Feb 2012
Posts: 19,320
Likes: 5,429
From: Rochester, NY
Bikes: Stewart S&S coupled sport tourer, Stewart Sunday light, Stewart Commuting, Stewart Touring, Co Motion Tandem, Stewart 3-Spd, Stewart Track, Fuji Finest, Mongoose Tomac ATB, GT Bravado ATB, JCP Folder, Stewart 650B ATB
Crank dust caps are not needed to have the bike work well. Many leave theirs off without issues. But the likely issue is that the extractor threads are cut off WRT the bolts being threaded into the spindle and bearing down on the arm's seats. Have you tried different bolts or caps? Andy.