I changed the clutches in my 2007 Honda rancher 400, now when I put it into gear it lunges forward and moves on its own, it does shift through all gears though please help
Welcome to the forum. First, can you verify your exact model Rancher. The 2007 Rancher 400 is a TRX400FA or FGA (gps model), also known as the 400AT. But 2007 was also the first year of the 420 Rancher in footshift or ES model, but some guys simplify and also call them 400's.you need to adjust your clutch. there is a great sticky in the repair section on how to adjust your clutch.
I'm going to assume yours is the TRX400FA though, like mine. In that case, ignore shadetree's advise above because the 400FA has the hondamatic and only has a centrifugal clutch. There is no change clutch to adjust, and you can't adjust the centrifugal clutch. So with the symptoms you are describing, either your idle speed is too high, or you put your one-way bearing in backwards. My guess is you put the one-way bearing in backwards cause you said you just replaced the clutch. One way to verify if it is in backwards or not is with the engine off, and transmission in D, can you push it forward and does it freewheel? If yes, the one-way is in backwards. Also, since you said you can still put it in gear and drive it, how is the engine braking.
Now if yours is a 2007 Rancher Footshift or ES (TRX420FM or TRX420FE), then take shadetree's advice above and adjust your change clutch....