I'd imagine there would need to be a lot o radiant heat hitting it for there to be a chance for it to catch alight and as NormK said, the cold air and fuel mix passing through would have an active cooling effect on the elbow from inside which should have some effect on the resin's temperature. It's almost like a built in cooling system.
Thanks for explaining Mowerfreak. Hence the term "air-cooled engine". This rings true, because even though the intake pipe runs alongside the exhaust you can still put your hand on it after the mower has been running. Unlike the nearby exhaust of course. lol!
The problem is my homemade one runs even closer to the exhaust than the original, and almost touches it at one point. I guess I will just have to keep an eye on it.
Suitable replacement manifolds are hard to find and also hard to make. I spent a lot of time searching online for a replacement. Lots of generic ones out there for go-karts, mopeds, scooters, but nothing that would fit. Also the shapes were completely wrong. Another problem: The connections on the Southern cross are 42mm between hole centres. Most modern ones are 45mm and have wider diameter intakes. The modern ones also have different spacing on the carb mounts to the block mounts. So the only solution was to make one. Took a whole day. A word of caution: epoxy resin is noxious stuff, even if you are wearing a respirator! Work with it outside in the fresh air, not inside in the shed... or house. lol!
