How do I switch the voltage on a delta Dj20 8" from 240v to 110v
I had the same problem as you.
You will find these two links useful:
http://www.electricmotorwarehouse.com/motor_connection_diagrams.htm
http://books.google.com/books?id=DDsh3lPokL4C&lpg=PA100&ots=N26cU5VS66&dq=wiring%20standard%20single%20phase%20dual%20voltage%20motor&pg=PA101#v=onepage&q&f=false
The first link shows you the NEMA standards for wiring a single phase dual-voltage motor. In the 'Dual Voltage: (Main Winding Only' table, the numbers are the terminal numbers on the motor. You will see to the left the standard color coding for each terminal number.
The second link shows you how a two mains winding/one start winding motor is wired, using the same terminal number convention. Note that Figure 8-32 is mislabeled; The T2 at the bottom should be labeled T4.
The reason it is a bit confusing for 220V as factory wired by Delta is they switch the T8 (Red) wire with the T5 (Black) wire against what the name plate recommends.
These leads are for the starter winding, which is used to get the shaft spinning in the direction that you want. The nameplate on the motor is for clockwise (CW) rotation, but the motor as mounted in the DJ-20 runs in counter-clockwise rotation (CCW).
So, the starter winding leads are flipped to get the shaft going the other direction (see http://en.wikipedia.org/wiki/AC_motor#Split-phase_induction_motor for a brief discussion; important takeaway 'phase lag' generates a magnetic difference that gets the shaft spinning).
For the question you asked: For 110V wiring,you need line 1 (probably black from the switch, its not too important) should blue, orange, black and for line 2 (white from the switch) should be red, white, yellow.
If for some reason the motor runs clockwise, just switch the red and black wires.
To add, on my motor name plate, it spells out you need to switch these two wires for CCW direction.
Don't forget to review your switch too. Generally, the black and white wires are both wired through the switch (dual pole), but for 110V, you just want the black wire running through the switch, and the white wires twisted together. In theory, this should be shown on the switch, but I haven't opened mine up yet.