I have purchased a 12-tooth countershaft sprocket for my TL125 K2. It is a JT Sprocket (part # JTF259.12), but the threaded holes on it do not match up to the holes in the OEM part that Honda calls the

use a circlip in instead

My Tl125 came with a 52t rear sprocket, cant remember what was on the front. Seemed ok at the time.

I've got the stock rear and a 12 tooth front. Mine fit with the stock Honda plate but the plate does hit the chain a little.

You need a big circlip to fit in the groove that the standard plate fits into, About 15mm diameter if I remember correctly.