Hacker 2.0 manual gear, third gear and fourth gear. If you step on the accelerator deeply, you will hear the sound of dadada. It's not very loud, but it sounds terrible. Who knows what it is?

According to your description of the fault phenomenon, I think it may be normal. Step on the accelerator pedal deeply, and the throttle opening will increase, which will cause the valve foot to ring. This sound is what you call "da da da". Of course, a slight noise is allowed, but if it is loud, you should check it carefully. Your voice is not very loud, so there is no problem. This sound will disappear as long as you loosen the throttle slightly.