ORIGINAL: Don M.
Just visit the thread on the MVVS 26cc and see how much trouble MANY of us are having with "black goo" on our planes. I have never seen anything like it, the covering on the stab of my plane is completely discolored from it and there is no way to get it off. I have several glow planes as well as several gassers and with the proper exhaust the glow planes are no harder to clean up than the gassers. I have a pattern ship with a YS 140 / Hatori pipe that you can fly all day and not even have to clean it. Cleaner planes with a gasser is a myth if you do it right.
The black goo on the MVVS 26 should disappear once it's broke it. It's normal for this to happen while the rings are breaking in.
No doubt a glow engine with full length pipe is going to stay clean.
A glow engine has to put out more "goo" than a gasser. You're talking 20% oil for the glow stuff and 2% for gasoline/oil mix. Where it ends up is due to the exhaust system......