Messy little things!
The only option I have come across for not getting the mess from where the exhaust mounts to the cylinder is to cut a couple grooves into the exhaust manifold for the after market type exhausts that slip on and are held in place by springs to the manifold. In those grooves, I put high temp resistant O-Rings so you get a nice tight fit.
beyond that, stock always has some mess, and after market exhausts need some form of sealing to keep things clean. Tried chamber seal, but that was worse then without.
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Charles Gallant