Hi Colin, it might but it is very sticky stuff. I first came upon this use of silicon when I was either helping or acting as passenger for a sidecar racing chum (I forget which). I was wondering around in the paddock at lunch time, as one does. and got talking to a couple of chaps who were rebuilding the top half of their engine over the break. Sidecar racers are often not rich and do all their own work. These chaps were putting household silicon sealant on the cylinder head and exhaust joints and assured me that it lasted for ages. Later, and as an experiment. I used on on my twin exhaust threads and where the joints are in the exhaust system. No leaks and no trouble getting things undone later. The reason that I always specify clear is that I have another hobby of sailing in the Mediterranean and on boats one often has to re-bed windows or hatches to prevent leaks. One can always go for £20+ pounds a tube stuff but over the years I have used silicon. My experience is that if one uses a silicon with colour, white or whatever, it will not be very stretchable after one year of Mediterranean sun. If clear, or translucent as it is called in Spain, is used then it is still providing a good seal five or six years later. If one has to take something apart then the old mastic can be stretched to several times it relaxed length whereas if pigmented silicon is used then it will snap before it is stretched too far. Based upon this experience I have only every used clear on exhaust systems. I imagine that it could be used on a two stroke exhaust system but I would want to try to get it grease free first. Good luck and let us know how it goes if you try it.
