The cause of poor loading performance from the CPC 464 Plus is often a perishing drive belt becoming slack, or more commonly kinked where it has sat without moving around the drive pulley for 25 years or so. This kink then becomes a permanent feature of the belt causing it to jump and slip.
The small belt doesn't usually snap or degrade to the same extent as the main belt, but can slacken off over time and also start to slip.
These square section belts are newly made and as are as close as possible to the size to the originals, but made from modern, more resilient materials. They have been tested extensively with the CPC 464 Plus and work perfectly.
Please note - these belts ARE NOT suitable for the original CPC 464.