look for a farm wood chipper 
wood pellet maker

http://pagead2.googlesyndication.com/pagead/ads?client=ca-pub-8290526608142878&dt=1223505992989&lmt=1223505992&format=fp_al_lp&output=html&correlator=1223505992989&channel=291%2B3026183983%2B9725417423&url=http%3A%2F%2Fwww.wisegeek.com%2Fwhy-is-a-carburetor-needed-in-a-gas-engine.htm&ea=off&ref=http%3A%2F%2Fwww.google.com%2Fsearch%3Fhl%3Den%26sa%3DX%26oi%3Dspell%26resnum%3D0%26ct%3Dresult%26cd%3D1%26q%3Dwood%2Bgas%2Bengine%2Bcarburetor%26spell%3D1&frm=0&cc=99&ga_vid=628316667.1223505736&ga_sid=1223505736&ga_hid=384006216&ga_fc=true&flash=9.0.124.0&u_h=864&u_w=1152&u_ah=836&u_aw=1152&u_cd=32&u_tz=-420&u_his=6&u_java=true&kw_type=radlink&prev_fmts=728x15_0ads_al&rt=ChBI7ThJAAAUGgpqBxj8QE43Eg5HYXMgQ2FyYnVyZXRvchoImhGgs16ouR0oAVITCJbz34DbmJYCFQVMagodgC-F5w&hl=en&kw0=Gas+Carburetor&kw1=Tecumseh+Diagrams&kw2=Carburetor+Engine&kw3=CNG+Cars&okw=Gas+Carburetor

good vidio and basic discriptions of types 
http://victorygasworks.ning.com/video

http://victorygasworks.ning.com/video/video/show?id=2209188%3AVideo%3A166