I dident have a noise I think just the bike struggles to move untill rpm increasesA lot of people think lugging is just low rpms. Lugging is when the rpms drop low enough that the engine makes a HORRIBLE noise / knocking, you will know it when you hear it, it sounds awful. It's the sound of so much pressure in the cylinder slamming the connecting rod and crank, because it's taking so long to open the exhaust valve. I am actually not sure what breaks first from excessive lugging. Maybe a bearing?