Hello again. The Enya 15 and the OS 15 II that I had about the same time the Thunder Tigers appeared were also pretty hard to handle when they were new. Mind you, I was pretty new with engines at that time too. I found that the OS was very easy to flood and that the Enya was very hard to start initially but once they both had a few runs under their belts , they ran well. The trick was to use "port priming" (ie just wet the side of the piston with fuel) and not to choke the engine too much. The Enya ran particularly well and we used it in combat at the time. The main problem with it was that it was to light compared to the English diesels for which the models we were building were designed. We were not very bothered by C of G and as a result the models with the Enya in them were very unstable. When we started using Super Tigre G15s, the balance problem went away. We used to run them on either 3 to 1 or 4 to 1 fuel with no nitro. I think I mainly used 3 to 1 which is 25% oil. And we always used castor oil. Synthetics were unheard of at that time. Bye for now. Michael from Oz