FROM BAD TO WORSE
Can rule out the decompressor, replaced it with a spark plug.
Checked for air-leaks, can't find any so rule that out.
What happens now is that the mower starts, splutters for a second or two and then dies. The obvious diagnosis is that it is starving for fuel so I again clean the carby for the third time. There is no change in the mower's behaviour, it starts, runs for a second and then dies. The spindle that the float pivots on looks like some brazing rod, perhaps it is not quite long enough and slips off, I don't know?
Have spark, compression but still doesn't run, tank has plenty of fuel. Any suggestions???
