I picked up a green Grand Prix with cottered cranks (probably from 1970). The cranks are securely attached to the spindle, but here's the problem. The spindle rotates about half an inch when moving the non-drive side crankarm forward and backward. On the drive side, the spindle doesn't rotate but the chainring/crankarm has movement left (towards the frame) and right (away from the frame). Does anyone have an idea what's going on? (Ideally I want to fix the existing bb/spindle rather than mess around further with the Raleigh proprietary bb.) Thanks.