The Grandsons Yamaha 125 has no oil filter but has a gauze arrangement. Chinese scooters are another engine with no paper filter. I suppose they were designed for throw away when it goes wrong.
Many of the 60s Hondas had camshaft failures as the cams ran direct in the alloy head and owners neglected oil changes.
Mainly the Benley twins that the learners rode at 10,000 rpm.