I have the same issue right now. I'm trying to diagnose this. Is that a tensioner issue? Did you fix the issue? I assume you did as this was a while ago.Here's my problem the bike runs great but it has a loud winding sound that gets louder and quieter as my boy speeds up and slows down. I believe it's the bearings in the wheel on the drive chain tensioner. Does that even make sense?
I recently took a link out of the chain b/c it had some slack and kept slipping off (the tensioner was all the way tight too) so after I took out the link and the chain is snug now it makes the noise.
I believe the chain was loose and the tensioner wasn't spinning.... and now it is.... because the chain is spinning it....???
Again new guy here! Thanks for everyone's help!