We have sucessfully used a few different brands of citrus-based solvent to remove oil from class F machines without problem.
It does depend on the construction and isulation type: for example polyimides and epoxies are very resistant to most common solvents, so unless you use something really aggressive like methylene chloride (dichloromethane) you should be ok on the common insulation types. If it is a very old machine then the insulation materials are likely to be far more susceptible to solvent attack.