What about having a fuel filter between the stop cock and the carbs ? At least they won't get shitted up ?
I was pulling your leg If I remember my chemistry correctly a strong alkali ( such as hydrogen peroxide ) gives you aluminium salts and hydrogen. IIRC alkali are more reactive with aluminium than acids.
Think I need to fill it with lemon water again and put the whole contraption on the hob, now that’ll be a sight for sore eyes , a nicely painted bike petrol on the gas burner!!