Nilfisk vacuum voltage conversion

I am converting a Nilfisk CDF-2040 back to 120 Volts after a factory conversion from 120 Volts to 240 Volts. This model has a dual speed switch. The factory returned the 120 Volt motor after the original conversion.
The conversion involves swapping the motor and is straight forward except for the dual speed feature. On the speed switch printed circuit board (hand marked "220V" with a magic marker) is a small adjustment.
My questions:
Must I change that board to a 120Volt version or is re-adjustment all that is necessary?
When re-adjusting, what is my criteria? I am familiar with the design of this type of speed control, but I don't know if this one is designed for dual voltage use (one needs more current at 120V) or what the lower speed is. In its current state (set for 220V) the motor will not run at the lower speed.
Thanks.
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Contact the Co , you have a 50hz- 60 hz difference if its Euoropean I dont know if it will work, If you mean a Europe comversion
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