The rod listed by Yamaha for CT2s and CT3s has a 3R2 prefix and the rod listed for CT1s is a 248. All my CT2 and CT3 motors have 248 rods so I'm assuming that all CTs originally came with the 248 rod.

I need to order the correct small end bearing for my CT2. Yamaha lists 2 part numbers (93310-216E1-00 and 93310-216L2-00 ). I have a Pro X replacement 3R2 rod (I'm not replacing the rod) that comes with a small end bearing that is 2mm narrower than the old one on my bike, i.e. a 3R2 rod bearing is 19.38mm wide and the one that came on my 248 rod is 21.82mm (see photos).

So do the two small end bearing part numbers default to the same bearing and, if so, is it the narrower bearing or the wider one? Does it make a difference if I install the narrower bearing using a Yamaha piston (see photos)?

While there are many variations in design, all the 125 and 175 Enduros used the same rod from 1969 to 1981. The YZ125 and IT175 used the same rod in the early years too.

3R2 is a good design and will work in all the above engines.

The small end bearing width has nothing to do with the rod, it's about the piston. The 125 uses the narrow bearing and the 175 uses the wider bearing.

175 takes the 93310-216E1-00 bearing... I would not use the narrow bearing.

Thank you MarkT for your help!