Just my 2 cents worth:
The 8 track motor *should* be fine, I have been keeping one aside myself for just such an application. I can only assume that Peter thinks the motor may be faulty, i.e. brush wear, bearing failure etc.
His suggestion of an AC synchronous motor is fine, but if you use one you won't need to use the club circuit because it will be "sync-ed" to the mains supply. In fact you can't use the circuit as it is intended to be used with a DC motor. Unfortunately, AC synchronous motors are generally hard to find and tend to be very expensive when you do (unless you use a bicycle dynamo or stepper motor - both with their own "nuances").
There are many members who have used this disk with cassette motors with success, one on this forum that springs to mind is Andrew, the site "owner". His "construction Diary"
http://www.taswegian.com/NBTV/forum/vie ... ry&start=0
should give you many suggestions of how to "debug" your system.
Keep in mind that it is not unusual to have problems "tuning" this circuit with your motor/disk/drive arrangement. Unfortunately it is not a "plug and play" type circuit as all the components disk, motor, bearing, belt, play a part in it's performance. Keep at it and I am sure you will get it working.