I read some of the RC forums about the ASP engines. The assessments were that they were pretty good engines but the bearings were cheap and wore out quickly. Better aftermarket bearings look to be available.
I made contact with the guys at Just Engines since their website shows CL versions of the ASP engines. The guys at Just Engines said the ASP is suitable for CL out of the box since the timing is conservative. All that is needed if you don't want to mess with the carb is a venturi and needle, which they can supply.
I thought I would take a chance and bought an ASP 46 from Hobby King. The needle and venturi I bought from Just Engines. I could have bought both engine and needle/venturi assembly from Just Engines but I wanted to see if, by chance, I might already have what I needed to make it CL worthy without the carb. But, since I had nothing on hand for the ASP I got the venturi and needle from Just Engines.
The ASP 46 is more like the ST 51 in outside dimensions. It weighs 12.6 ounces with the venturi and needle assembly but without any muffler. It is longer and wider than the LA 46 so nothing in my fleet is a suitable test bed aircraft for testing the engine for CL use. I can't remove the LA 46 and install the ASP without some structural mods to existing planes. If I think about it more I can probably come up with something but I have other projects to finish first.
I would bet that the power of the ASP 46 would come close to that of the ST 51. The largest plane in my fleet now is about 570 squares and 55 ounces total weight. The LA 46, with some minor mods, hauls it around just fine. So, I think something like 600+ squares might be an appropriate size plane for the ASP. Until I get around to making the mods to an existing plane I will never know for sure how it will perform as a CL engine.
Someone in my area might have a plane that they are willing to use as a test bed and if so I would be willing to have them install the engine and we can see how it goes.