I have a Mountfield mower (originally bought from B&Q around 5 years ago) which has a Briggs and Straton engine. All has been well until 2 events... 1. We had a load of building work done and the mower got piled under some other gardening gear and the 2 springs on the carb stretched (net result mower would start etc. but not run so smoothly) 2. The builders used a fuel can for Diesel and I mistakenly put it in the mower :(. Net result tried to start mower (obviously failed miserably) realised my mistake, emptied the tank, filled with petrol. Mower eventually started and I mowed the lawn (albeit with clouds of black smoke!!).
I used the mower a few times after the diesel episode, and although on starting it would have some black smoke, during normal operation, it was smoke free - still not running right though.
All of a sudden, it started conking out after around 10 mins of usage. Taking the plug out revealed it was caked in soot. Cleaning it got the mower going agin for 10 mins... So I... 1. changed the springs on the carb 2. cleaned the air filter 3. replaced the plug 4. got fresh petrol
None of this seems to have made a difference except for the running duration has gone up from 10 mins to enough to mow my lawn (probably an hour and a half or so). Recently though... the 10 mins duration has returned and the same coked up plug and clean remedy!!!
Anyone any idea what I could try next? Should I scrap it?
thanks in advance for your help