Omg, there is a knock in my engine and a squeak in my rear wheel. There's two things I'm not good at. 1. Opening the bottom end of these engines. 2. Overhauling coaster brakes. What did I do to fix it? First I focused on the squeak, must be my pads or bone dry in there. Replaced the whole coaster brake assembly and took the rear wheel in to have them dial in correct tightness on the axle. After a 3 foot test ride... It's still squeaking. I open my 3bolt panel to throw some Lithium grease in there, now I know the sound is coming from the chain and figure it's not gonna hurt things to eliminate the clutch pin as the culprit. And that nut that holds the drive axle in FALLS OUT. Omg, right? I apply some grease under the clutch pin, put the nut back over the sprocket and oilah. No squeak, no knock. Solved. The entire culprit was that drive sprocket area, the loose nut made an engine knock sound and the dry clutch pin made a squeak, simulating two entirely different assumed errors, the chain carried that sound to areas of the bike and I misdiagnosed and mistreated it. But I solved it at the end of the day, and it seems to be good as gold now.