Like Droogs I use a sonic cleaner. It's mainly for cleaning airbrushes but I have an assortment of fluids I use for various uses. I have small and medium size nylon seal bags. I put the cleaning fluid which maybe brake fluid, cellulose thinner, washing up liquid, baking soda, citrus acid or to answer your query, left-over two-stroke. I put the item in the bag along with appropriate fluid, seal it and put it in the water bath of the sonic cleaner set to around 50C. Around ten to twenty minutes in there usually does it. The polythene bag will break down with any petrol based fluid but will give you more than enough time to clean 'your bits' with and rather than glass jars that I hear some sonic cleaner users use. The bags won't hinder the the effectiveness of the cleaner.