My motor has done approx 20 hours since rebuild, mainly cross country events/enduro.
When i rebuilt it i struggled to get brass caged M25 crank bearings, so i brought some 'european' quality bearings with a polyamid cage.
Yesterday, some 4 hours into a 6 hour enduro, the engine made a hideous noise and ground to a halt. I initially thought a ring had picked up and broke, however after stripping it seems the bearing cage has disintergrated and ground the crank to a halt (i say this as i was picking the bits of plastic from out the transfer ports last night).
Has anyone else had a bad experience with polyamid caged M25 bearings? I am considering rebuilding with 2 part roller bearings like in the modern KTM 250/300's
Any advice?