I need some help. I have a Troy bilt push behind 21" 190cc 6.75. It was turning on fine but over reving. I did a small tune up and changed the oil, plug, and filter. Now it's almost impossible to pull the starter rope. After watching some videos I saw the mention of hydro lock. When I remove the plug the string pulls just fine. I pulled it a few times trying to remove any fluids as suggested but nothing came out. That's one issue. I did somehow manage to get it on once after a good struggle. The rpm's are still super high. There is a bar on top with a spring that I moved manually and the rpm's went down. I'm not sure if the spring lost tension and that is what maintains correct rpm's? It's about 8 years old. Worth saving?