Beard, Hi And Welcome. There Should Be Several Atemps For Saw Mounts On Here. Chain Saw Motors Are High Quality, Sthil Being About The Best. Boygofast Has Just Got A New Batch Of China Girl Kits In, 49cc, Steel Sleeve Cylinder, Slant Head With New Style Carb = $117.99. That Is Hard To Beat. "davidsfarm" Has Saw-bike Video`s On - "you Tube Video's" I Spent A Lot Of Time With The Chain Saw Idea, And Gave Up. Here Is A New Idea, Just Popped Into My Head ( And I Have Not Even Had My Morning Coffee). The Main Problem Is The Engine Rotation. Use The "golden Eagle" Belt Drive Parts. The 31cc Saw Motor And It`s Rpm Range Should Be Perfect. They Use Direct Drive, No Gear Reduction. The Very Large (about 18" Dia.) Nylon Cogged Sheave Snaps Onto The Spokes, The Approx 1" Dia. Drive Pulley (cog) Has A 5/16" Nf Female Thread (right Hand Thread). Golden Eagle Is A Very Proven System. The The Belt Is $25., The Top Cog Is $25. And The Large Sheave Is Around $40-$50. Now You Have To Mount It On The Right Side.your Peddal Chain Is Going To Be A Problem, To Clear The Nylon Sheave. Maybe Reversing The Sprockets On The Rear Cassette Would Work. (put Large Sprockets To The Outside For Pedal Power, So Chain Will Miss The Scheave. Dam, The Drive Pulley Will Screw Off The Crank. It Would Have To Be Welded To Saw Clutch Drum. I Think Your Sthil Has The Sprocket On The Outside , Which Helps. I Am Figuring This Out As I Type, Never Thought Of It Before. D Bore Cogs Are Available From Suppliers. You Need To Use The Clutch. They Are Tough. I Need My Coffee Now!! Lol. Well, Something To Think About Anyway. Saw Motors Are Difficult To Mount. Have Owned A Tree Service For Over 30 Yrs = I Always Say: Chainsaws Are Like Women, A Good One Is Fun, A Bad One Will Drive You Nuts!! Imho Ron .
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