RE: OS .15 Steel Fin?
Hello Lomcevak, I still have my .19 which has steel fins on the cylinder. Maybe you have just the .15 version. We ran these engines on 75% methanol and 25% castor, no nitro. Throttling was just fine, with the baffle or with a muffler, but a glow plug with an idle bar helped. The muffler was made by OS and had no pressure tap, just a bushing for priming the engine with a long needle on a syringe. The carburetor had enough suction to do without tank pressure if only the tank was at about the same level as the carb.