RE: Hirtenberger .61 with a sliding piston carburetor
I am quite lucky in that the original manual came with the engine. The manufacturer indicates that the piston carb "injects" additional fuel into the intake manifold when it is rapidly opened. Naturally I will try to verify this when I have time to attempt starting and tuning the engine. As far as the glow plug is concerned, a "long reach" plug is recommended. In addition a colder plug is recommended for higher nitro content while a hotter plug is recommended with lower nitro. Comparing the OS "F" plug to a "#8" plug, it appears the filament should extend further into the combustion chamber with the "F" plug. The "F" plug should be a pretty hot plug since it is recommended for four stroke engines. I have never ordered a Merlin plug and it is difficult to see from the web site, which might be a long reach plug and which are not.