Bearings

Nomenclature

The first set of numbers indicate the bearing sizes and type. For most moped purposes bearings will be metric single row bearings. The next number is seals. For engine crank bearings, unsealed is important to allow lubrication of the balls in the bearing. Often the seals are plastic or rubber and removable but avoid metal seals. For external bearings such as for Sealed bearing conversion of wheels, having bearing seals is advantageous to keep out dirt and debris. Regarding the internal clearance, this is VERY IMPORTANT for engine bearings. Because they expand when hot, for engine bearings a C3 clearance rating allows expansion of the bearing to roll smoothly and not bind up.

Additionally it is good to check the RPM rating of bearings, and any additional information regarding loading. Some high quality bearings may only be rated to 1000rpm and despite being a good bearing will fail quickly in a motor. Likewise sometimes the bearing cage materials may be plastics which are not heat tolerant or gas tolerant. Always check

Table of Common Bearing Sizes

This is a list of commonly used bearings and their dimensions. Dimensions are in millimeters. See also the Bearing and Seal Chart for a more comprehensive list for specific brands and models.

ID	Inner Diameter	Outer Diameter	Width	Usage
L17 (FAG)	17	40	10	ZA50 magneto side crank bearings
E20 (FAG)	20	47	12	ZA50 transmission side crank bearing
6002 (ISO)	15	32	9	ZA50 transmission cover crank side
16101 (ISO)	12	30	8	ZA50 transmission cover intermediate side - oil injected
16100 (ISO)	10	28	8	ZA50 transmission cover intermediate side - non oil injected
6005 (ISO)	25	47	12	ZA50 intermediate shaft main
6203 (ISO)	17	40	12	ZA50 output shaft main
HK 1816 (FAG)	18	24	16	ZA50 output shaft roller
HK 1612 (FAG)	16	22	12	ZA50 second speed gear internals

ISO FAG

online bearing store: http://www.vxb.com