I had the same problem. Luckily, Amazon.com still sells this model and has the manual in .pdf format. You can find it here.
http://www.amazon.com/Ryobi-700R-2-Cycle-String-Trimmer/dp/B000087QX2/ref=sr_11_1/002-5256994-2918455?ie=UTF8
Enjoy!
Everett
April 2007