JAP

Hi, did you have any luck? my problem was I was using a bike chain lube that was too thick and not penetrating the links, therefore dry chain internals. Hence change to WD40 , plus chain tension needs to be a balance between all areas when you rotate wheel as there is tight spots. I hope this solved your problem, let me know.

Had a similar noise from a 16r few years ago and same tight spots when turning wheel. I'd recommend taking chain off and cleaning with petrol and then re lubing with wd40. Try the motor to check for noise with chain off. When re setting chain tension turn wheel in case of chain tight in particular area and adjust accordingly. My experience was a dry chain interals and tight in areas, I was convinced it was bearings., Been fine since with WD40 as chain lube. Oset always helpful themselves. Hope this is worth a try.