Motorcycle Questions? Ask a Mechanic.
Hi and thank you for your question.
This sounds like a fuel supply issue.
Since you have 2, and one is running normally. I suggest swapping the carbs between the 2 units. If either bike will run on the one known good carb, then the 2nd carb is going to have to be repaired. If the 2nd non running bike will not run with the known good carb, then we have other issues. We will need to dig deeper into the ignition and mechanical aspects of the engine to determine where the problem is.
Let me know what you learn from swapping the carbs.