Speed only works on highest setting on the dial

"@freddifrog this is most likely caused by a failed spark suppression capacitor for the governor. IF it fails your mixer will only work at full speed. Check for it under the cover on the bottom of the motor. You’d be looking for a small, round, aluminum can looking part. Post some images of what you find so we can assist you further with that.

Here is Untitled the service manual to help you with your disassembly etc."