Installation of Model Engine Bearings Installation of Model Engine Bearings Over the years, people have offered advice to me about how to replace bearings.
Perfect installation is much more important here than with the larger engines.
Why, because the little engines have so little excess horsepower. They use ALL of the output. If something is not perfect, the engine will show it more emphatically than the large engines having a lot of excess horsepower. Selection of the replacement bearing is important. Use either a grade 3 or 5 bearings, so that you have tolerances that are correct.