My neighbor gave me their old John Deere SRX75 with a Kawasaki FC290V engine. Was not running. The cooling air intake was quite obstructed, and the oil level was very low. Had not run for years. Compression is good, ( 175- 195 , cold ) - after new air filter and fresh fuel, started right up. Changed oil with 10w30 Valvoline MaxLife. Starts up instantly, seems to have good power, but has a noise- maybe a bit louder than a tick, but not ( to me ) a conclusive knock. I was thinking of draining and changing to 30W. I am about $80.00 into it, the idea was to fix and sell, but do not want to sell someone a problem. By the way, used it to mow my back lawn, noise did not get louder. Any ideas ? Thanks