Carb problem

[Tony Griffiths]

Thanks dickie65 and andrew34ruby - that's a good idea but not the case here. The next day, with a stone-cold engine, the situation was the same - tickover but no revs. I have a Chummy with a SU carb and 4-branch exhaust - an arrangement that lacks a hot spot - and that suffers from carb icing. The previous owner thought that the misfire might be because the petrol was boiling, but when I looked during a run, there it was, a carb covered in ice. The solution was to wrap copper wire around two of the exhaust pipes, and from there around the 'inlet manifold'. Problem solved. As a flight instructor once told me when we were discussing carb icing in light aircraft - it's always winter inside a carb.  Even at temperatures exceeding 30 °C on humid days, the drop in temperature between the inlet and the venturi can lead to icing.
Incidentally, many pilots have lost the plot when, suffering from icing, they've switched to hot air and despaired as the engine ran even more roughly as the ice melted. In a panic, they turn the hot air off, only for the engine to stop and refuse to restart. At least we can park at the side of the road....