Oracle Delphi Mk I motor and PS upgrades

You can try and mount the VPI Scout or TNT motor, or a Basis motor and then just change the pulley to get the speed where you want it. Its just a mathematical calculation to determine the pulley diameter to use with any platter diameter. If you use a VPI SDS you might not even have to change pulleys.

Have you tried the speed adjustment screws either on the back of the motor mount or on the left side of the front speed selector mount? You should be able to get some speed adjustment from those.

Ok, then try putting a layer of tape around the part of the platter that the belt rides on. This makes the platter circumferance bigger, which would slow down the platter. YOu may have to use more than one layer. masking tape works fine, but make sure you clean and degrease the area so it sticks well.