As summarized, I'd like to run a 240 volt motor with 3 prong twistlock plug off my
Generator that has a 240V 4 prong twistlock outlet,
Have purchased a 4 prong dryer plug & cord. Not sure what function the extra lead performs, any help is greatly appreciated, Thanks...

Apologies, searched for previous posts,
Couldn't find any until I posted Question, Thanks

Posts did not clearly answer my question,
Answers would be appreciated!!

On the generator you have 4 leads. Two are hots, a neutral, and a ground. On the motor you should have, two hots and a ground. A 240v motor does not need a neutral, some appliances, or if you want to run anything 120v, you will need a neutral.

Why did you get the dryer plug/cord?

To just run a motor get the proper 4 prong twist lock plug that fits your generator and put it on the cord to the motor. You do not connect anything to the neutral connection, leave it blank.

Thanks MEDIC-DAN,
Got the 4 prong dryer cord as that is what fits the generator, just needed to be sure what
leads went to what prongs,
I gather that red=hot, black=hot, green=ground, and white=blank.
Appreciate your help!!

I have a welder I'm wanting to run on a 240v 4 prong plug. The welder runs on a 240v 3 prong. Do I just to the same thing? Use the 2 hots and not neutral wire?

I would first check you welders amperage draw,
https://www.askmehelpdesk.com/electrical-lighting/wiring-3-prong-plug-4-prong-outlet-226475.html
Most Household circuits can't handle it.
If your circuits are capable, search for an answer to your wiring question or post a new thread.
My knowledge doesn't cover your specific question.
Happy (and SAFE( Holidays!