Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

I have a Mamod Challenger also. Mine is one of the early ones with the stainless-steel piston/rod and squared cylinder. It does have a slight bulge in the boiler barrel, I think that's where the end cap is. It doesn't have the problems yours is experiencing, but a word of warning about the gas tank. I bought the gas scuttle also and this tank as well as the one on the SP8 I have leaked gas out of the stem (and lit up!). Both have been replaced with BIX tanks. BIX tank threads are not compatible with Mamod pipework, so that had to be changed too.

Due to these glaring oversights by Mamod, I'll never buy another one.

I knew I should have gone with a Bix burner… 

Mine leaked a little after the first fill… I filled it outside and wiggled it with my finger and the leak seemed to stop. Guess that’s what I get for trying to save a little money…