Hey got a ?

Question

you see i only got 370 miles on my new bike but three days ago i notic that three of my teeth on my big cog is smaller than the other the chain dose not skip but is the cog worn

Answer 1

As tom said this is normal. The teeth are of different size to help shifting. You'll see a different shape as well. If you look closely you will note ramps on the side of the cogs as well.

Answer 2

I have seen some (not many) sprockets which have smaller teeth to help with upshifting to a lower gear. It might be a case of this.

You replaced the chain since you got the bike? A new chain on a used cassette can mean a higher rate of wear on the casette