Small Engines (Lawn Mowers, etc.): Briggs 3.5 wont start, engine model type, brigges and stratton

Question
Hi

Yesterday i started up my 3.5hp brigges and stratton for the first time in about a week and a half on fresh petrol . It was reluctant to rev and would only run smooth on low throttle(it has been doing this for a while). Having eventually finished the first lawn i let it cool down then found that the spark plug was nearly completely black. I cleaned it and tested it and it had good spark. I put the spark plug back in and checked the oil which was a shiny black colour (probably needed changing). The carb was also clean. I put the thing back together and tried to start it. There was one fairly loud pop and i found that the spark plug was covered in oil. the compression was slightly lower than normal.
Any ideas?
Thanks, Richard

Answer
Have you tried a brand new spark plug?  Since you mentioned the idle issue this may be an indicator of a dirty carburetor.  I will need the engine model, type and code number to look up your carb.

Try a new spark plug and see if it will start.  If it will not start then remove the air filter and try spraying a little starting fluid in the carb and see if it will start.

Send me the engine info.
Eric