Did you ever solve this one, I have a victa mitre master deluxe that has the exact same symptoms, cold it may start, splutters and chugs for 5 seconds and then dies off. Operating the throttle does not seem to improve it. In my case have not cleaned the carby yet, mower was left under a tree for a few years. I did remove petrol tank and clean it out - had signs of water - milky.
