I need to make a Venturi for an OS 15 FP. what is the stock diameter of the bore?

Thanks 

Not to topic drift, however; Randy do you know if that will also fit the OS max III 15? I can post a pic or measurement. Thanks!

              Larry, the throat size is .236". The spraybar for the LA/FP .15 is not the same as the .20-.46 spraybar assembly. It will fit but it will also take up more volume. The stock FP .15 spraybar is turned down. If your using the nozzle that comes with the remote assembly, this should be irrelevant. I have opened the throat to .250 for clown racing and it still worked fine on suction. Ken

              Larry, the throat size is .236". The spraybar for the LA/FP .15 is not the same as the .20-.46 spraybar assembly. It will fit but it will also take up more volume. The stock FP .15 spraybar is turned down. If your using the nozzle that comes with the remote assembly, this should be irrelevant. I have opened the throat to .250 for clown racing and it still worked fine on suction. Ken

  I would not recommend that for stunt!  As you found it works fine for level flight at high RPM, but for stunt, the stock venturi is absolutely as large as you would ever try to run and only then when you let it run to at least moderate-high revs by stunt standards.

   The very first engine in the "small engine" experiments was the 20FP, but what kicked it all off was a bone-stock 15FP in a (regular S1) Ringmaster, which David and I marvelled at when some gentleman brought it out to fly with us in Napa.

     Brett