Vintage Dirt Bike Q & A

I've been riding my 75 MT250 to work for the last week, and it had a pretty good failure today, it lost the chain on the way home. Luckily it was only at 35, and I could immediately get off the road, and I knew this sort of thing wasn't too far off since I found a couple missing rollers the other day. Still, a big disappointment after all I've put into it so far.
An issue that I've found is that the drive sprocket seems to move quite a bit on the shaft. About half the tooth thickness of the retainer is gone, so this may be contributing to it, but the sprocket doesn't really look worn. I know the worn cush drive on the rear hub isn't helping either, but nothing I can really do about that now.
How much wobble is too much on that sprocket?

Never measured it. But there is some as you know. Problably less than 1/4" at the tips. But no matter what you think by looking, if you were running it with a chain damaged enough to be missing two rollers, it is time to replace both sprockets. If you replace the chain alone, it will last about six months tops with casual riding. The front sprocket is only about $14 or so. Good luck.