I have a Yardmachine 21" with a B&S 550ex, engine model #09P702-0145-F1, Serial #1608165118199. Starts first pull, runs great untill it gets hot (about 4 or 5 minutes) and starts acting up. Sounds like it starts running a little rich or is missing. Has new plug, air filter and fresh gas. Tried removing gas cap to check for cap vent. Checked valves, set at .006. The intake valve was tight. I believe they are supposed to be between .004 and .008. Could use a little help.
Thanks,
Pat Pitts