@mjmikey Koyo bearings are very good quality but did you order the correct ones for this application? I believe for crankshaft applications they need to have larger clearances to allow for heat expansion; PJME refer to this as "the correct R1 type" but I've also heard it referred to as C3/C4 clearance:
https://www.pjme.co.uk/acatalog/Yamaha-DT125LC-Crankshaft-Main-Bearing-RH-5698.html#SID=103
M
