Good quality engine sprocket source?

I don't think a carbide bit will touch it.
Sprockets are hardened, real hard. A file will not leave a mark on them.
Plus it has a keyway in the taper, so trying to bore a hole in tough/hard steel with an interrupted cut, sounds like it would be chatter city on my old Drummond lathe. (It is older than the bike!) And you know what carbide is like re impact on odd shapes etc, tends to get chipped at the cutting edge.

Of course, I could heat the sprocket up with the oxy and normalize/anneal it with slow cooling, but not knowing the makeup of the steel, or even whether it is case hardened or quenched, it would be pretty dodgy trying to reharden it without going too brittle or too soft. That is why I was thinking of grinding it, that plus the finer surface finish you get.

The new sprocket taper is correct size at the small (outer) end but is .031" undersize on the large end of the tapered hole.
As it is, the sprocket will only go about halfway on to the shaft before the undersize large end of the hole hangs up on the shaft taper. So there is too much metal still in the large end of the hole.

So I need to remove about .030" inches (diameter) of metal from the larger end of the hole, then it will slide right on to the correct position.

Still waiting to hear back from both my suppliers about this latest pair of dud sprockets.

[Pa]

That tool will cut it but the machine must be rigid. Grinding is all well an good as wel...l but.... whether using a cutting tool or grinding, you should fill the keyway to eliminate the interrupted cut or grind. If you cut, feed the tool at .005" travel per revolution and run the tool back out at the same feed rate. This will leave a fairly smooth finish for lapping the taper to the male taper.

... whether using a cutting tool or grinding, you should fill the keyway to eliminate the interrupted cut or grind..

Now that is a good idea. A bit of key steel stuck in there with green super-strenght loctite would do the job. Brilliant. Thanks.

Well a happy ending to the sorry sprocket saga, my suppliers sent me a new sprocket, this time made in India, not in Taiwan by V-Twin Mfg. The Indian made sprocket is visibly better machined - has the properly ground taper, covered in cosmolene type wax to protect it and ensure precision fit. And the Indian job is the correct dimension. Fit right on.
The old bike is purring along much smoother on the open road now.
Only thing is, I can't tell how much the 33T sprocket increased my cruising speed because my speedo drive gear up and died as I rode out the driveway!

Anyhow, here is a pic of the the two sprockets, and how to easily tell the good from the bad, other than by the quality of finish on the taper. The good sprocket, left, has a raised boss in the centre, while the Taiwan trash, right, is slab-sided in that area. Avoid the latter.


And here is my jury-rigged lathe set up to regrind the taper if I had to - but my flexidrive is too loose and sloppy in the end bearing, so I'm glad the suppliers sorted things out before I had to get this desperate.

[Pa]

That is great news and thanks for the supplier reference on good sprockets ! I like you grinding set up as well but glad you did not have to do the task. Pa

That is great news and thanks for the supplier reference on good sprockets ! I like you grinding set up as well but glad you did not have to do the task. Pa

Yep. Both 45 Restoration Company and ThrottleMasters on eBay sell the good-quality dished-style sprockets.
As they say on TV, accept no substitute!