I am in the process of replacing back tire on my project AT1C.  I have ordered brake shoes for it as well as they were wore out.  I also need to order a sprockets and chain as the back sprocket appears to be in pretty bad shape.  I have counted the teeth and i get 14 on the front and 43 on the back.  I notice in the tech library it states 14 on the front and 45 teeth for the back is normal.  Why would someone use a 43 tooth sprocket?  The chain in the tech library states i need a 428-110 chain.  I plan to order the 14 for the front and the 45 tooth for the back along with the standard 428-110 chain.  Is there any reason to do any different?  Guess i will just search ebay and or amazon for the sprockets and chain unless someone has good reccommendations.  Thanks in advance for all help and advice,   

Two teeth fewer in the back would increase top speed, but it's usually easier to go up one in the front, as you only have to remove the chain and not the entire rear wheel. I'd go standard and see how you like that. You can always change the front by one tooth if you want later.

Thanks for the response. I will do as you suggest.

The stock 14/ 45 for me was too low geared.  Good for keeping max speed (60 mph) on level ground maybe but going down a grade or with tail wind it could use a little taller gearing to keep away from the redline. Yes you may have to drop to fourth gear on a hill.
 I’d suggest that if your chain and sprockets are “safe enough “,  you take a spin to experience rowing through the gears down the road a few times before ordering anything . 
  Second gear starts while slipping the clutch a little makes for smoother takeoffs from stop signs.
 

Thanks for the feedback Dave. Im going to have to try the 14 / 45 at least for a little as they are almost ready to be delivered.