I used carb cleaner. I sprayed loads of it inside and let it soak for a while, then used a toothbrush to get the crap off the inside. I had a small 12v battery nearby so I got 2 wires connected it to the correct +ve and _ve terminals and fired the ISV up for a few seconds to shift the crap inside. Again I sprayed more carb cleaner inside and repeated the process a few times and eventually clean carb fluid came out. Once dry and clean I sprayed a bit of WD40 to lube up the inside as carb cleaner leaves the ISV very dry inside.