I've got a 5hp engine on my Power Rake that has become almost impossible to start. I change the filter, plug and oil often. I even took the head off and removed the carbon and checked to make sure the valves were operational. I have tried starting fluid with mixed results. It seems to take alot of attempts to start it. I've had better results trying to start it with choke on then off, back and forth about 20-30 times with the filter off. The starting fluid doesnt seem to make too much of a difference. When I pulled the plug it seems to be getting a decent spark. When pulling the starter rope the valves seemed to operate properly. I also cleaned them up as good as I can. Unfortunately all of my mechanical experience has been with 2 stroke dirt bikes so I'm not at all familiar with valves. I have gone over everything I can think of with this engine, so I'm left guessing its needs a valve job. Is there anywhere on-line that explains this procedure. Can it be done without taking it to a shop? Sorry this is so long winded but I just replaced one engine and hope I dont have to do the same with this one Any suggestions??