Originally Posted by thirstybuck
The countershaft is in good shape. I still think that that is a hell of a lot of lateral play, but I haven't had to deal with countershaft sprocket before. The back and forth play, chain directions, is much better than side to side. Tell me what you think.
Hmm, looks normal – but as I said, the wear of the countershaft is crucial. It’s kind of hard to tell with the bare eye; before I took the picture I thought there was no wear. Only after zooming the pic I saw that the shaft lost actually some material. Btw, it looks like you got an original sprocket, since that is the only one that got that rubber mounts.
Honda used that "flexible" mounting of the sprocket on all dirt bikes of that period (dunno about the CRF etc.) and a lot of drivers got puzzled by that. I was told that the side to side play is necessary to counteract torsions of the frame/swingarm for instance during hard landings.
I heard of some problems with that flexible mounting on the much stronger XRV650 Africa Twin. Many drivers had to buy new countershafts, some of them tried to glue (no kidding) the sprocket to the shaft, but I don’t know if that is advisable. And there had been many discussions among XRV drivers about the quality of aftermarket sprockets, apparently some are made of harder steel than the shaft (JT), or are not made with the necessary precision (sunstar).
I don’t know if that is the case with the NX250, but given the consequences, I would go with the OEM sprocket (plate and bolts are sold separately). And a bit of grease and chain lube from time to time shouldn’t hurt ;-).