Briggs & Stratton Intek 206 Pro Engine Repair Manual?

I find the starter pull cord extremely stiff on my 2003 Briggs & Stratton Intek Pro 206 6.5 hp engine (fitted to a generator). When I remove the spark plug the engine turns over smoothly so I suspect the key on the crankshaft has sheared causing the valve timing to go wrong.
Where can I purchase a repair manual? If it helps, the engine cover has the serial number 121312 stamped on it and also 031027 PE.