I suspect you have a relatively recent issue S.45, an ABC Schneurle ported device. This engine isn't designed for CL, of course, but it should be possible to make it work for Sport-Stunt, at least. My fellow club member, Larry Price (aka Curmudgeon on SSW) has one, and asked what sort of setup might work on it. You two might conspire, tho I don't know how close Larry is to flying his.

I suggested using the MACS Muffler. http://www.macspro.com/onepiece.asp They seem to limit the peak rpm, but also need to be run in the right rpm range, which is around 10k, +/- a few hundred. I'd start with a .281" venturi with a .156" spraybar through the center, but it will run up to .312"+ with no problem. A Bruline air filter would be an easy way to tune the venturi size...coarse and fine filter elements. The coarse is about equal to .010" reduction, the fine about .020". Also makes the engine much easier to start, especially inverted.


A Thunderbolt, Zinger, or K&B 4 cycle glowplug would be a reasonable starting point, along with Powermaster 10-22 or similar fuel. That's half castor/half Klotz with 22% oil. The engine will have to be set rich at launch to prevent sagging overhead, so look for a peak of about 12k on 4" pitch or less. I'd be trying the APC 12.25 x 3.75, or 12-4 Zinger Pro, but would expect to clip it down some. It won't be the ultimate prop, but a good starting point (Square 1).

When the muffler (tuned pipe) is working just right, it makes a rattling noise, sounding about like the wheels are falling off. That's good. Unless the wheels fall off. I ran the MACS Muffler setup on my .46LA/Humongus, and it was absolutely the easiest setup to run, and with good fuel economy. But you need a tach.

If you can't make that work at all, I'd suggest blocking the boost port, running 5" pitch (12-5 APC or Zinger Pro) and a Randy Aero muffler. That'd be an SSW setup, which works well. The venturi would maybe get enlarged some, but everything else would probably work. It would take a lot more fuel capacity. Florida's heat and humidity would make me leave the fins alone...and keep them clean.   Steve 

Phil: FWIW The ST45 and ST 51 use the same carb. So the venturi from the ST 51 C/L and NVA will fit it. 9.00 for the NVA and 10.00 for the venturi through Tower.