I dont think its a good idea to ever assume anything
Thats all we can do when the OP didn't give the detail some others think they need.
The only flavor of three phase I am really sure about is 208 Wye that it does not have a wild leg. It is possible that the variety of three phase he is dealing with has a wild leg and if so, don't just pick any two legs to connect the motor.
Even if it was a Delta with a center tap, any 2 phases would still give you your 240v single phase. What your referring to is if you went from the grounded conductor (neutral) to the high leg you would have 208v.
Refer to post #10 we are only wasting time without any more details.
Wasting time only because I answered the OP's question in post #3.
Also, I don't believe it's a waste of time when some might be learning from the post's