Hi, I have a few 17 tooth sprockets for sale for the K157FMI engine found in models such as the Pulse Adrenaline. These are only sold in china as far as I know so if you don't want to wait the 2-3 weeks postage time to get one check out this auction.
http://cgi.ebay.co.uk/ws/eBayISAPI.d...m=280836052054
