The original rear wheel bearings are not great, it is worth replacing them if you have the rear wheel out. Also have a check of the rear swing arm bearings, particularly the LH one next to the bevel box sprocket. If it doesn't have a dust cover fitted (many seem to have been left off from manufacture) the bearings will be badly corroded. If the rear wheel drive sprocket is made of alloy, rather than steel, it will wear quickly and the belt will screech. The only cure is a new sprocket.
There is a lot of information freely available on the MTWC website 5 Speeder section :
https://www.mtwc.co.uk/the-5-speeder/ . The Alternative Parts List has many numbers for items used on the M3W as well, it's listed on this forum and the MTWC website.
