Hi I have a brand new Briggs & Stratton mower UK model as i live their. I bought the mower in a job lot so cant return to store. The return label just said 'Wont start'. It has a 300 series engine. I have put new fuel and oil in it but cant get it to start from the pull chord. There is a spark. I have noticed quite a large amount of oil on the air filter. I squirted a bit of gas into the carb inlet and it started first time. Any advice greatly appreciated and thanks in advance.