Andy
I only tried them as I couldn't find the small carb I was going to do. I had read the Kemet guide and they said

"In some instances burnt on carbon ie. cylinder heads, injection moulding/plastic extrusion dies with burnt on residue can very effectively be cleaned with ultrasonic action and the correct combination of detergent."

This was obviously not one of those instances or I didn't use the correct combination of detergent

Not to worry, I will find some other piece of kit to try out