So many have commented about zturns...this cam is from 23 hp Kaw( a common zturn engine) This is an object lesson in changing oil and filter often...300 hrs on this engine,oil and filter never change and never added to....the sludge residue finally kept the acr from moving at all..therefore almost impossible to start...the entire cam has to be replaced because the acr is built into it. That means removing tension from valves etc...quite a job,not cheap if you're paying someone else. ...the replacement engine was $1700.....so there's the lesson....6 yr old machine...any questions??