I have 2 new (4 weeks old) Runner 2, one is quite and the other sounds like what your describing when using Pas2 or higher and with Throttle only. Rad gave the same response. After a few messages and phone calls, Rad gave me a warranty code for one hr work at bike shop. They realigned chain alignment thing & Crank arms. Still have the noise??.Yesterday got a message, Rad sending out new Back Wheel/Motor under warranty! Keep calling and messaging them, it?s frustrating to say the least