this sounds like your clutch is sticking,it could either be a build up of dust or possibly a clutch spring broken.
there are usually 3 springs on the clutch and they are penneys to buy.
you would find your clutch situated at the engine end of your machine,you need to remove engine from the shaft by undoing the 4 bolts round your engine.you will then find the clutch drum covering the clutch.once you look into the end of the drum you will see a bolt inside(not sure what size this is they differ).remove the bolt and you then have access to your clutch
i hope this is useful for you.
wayne, August 2008