I was in a tinkering mood yesterday and I decided to satisfy an old curiosity, mainly the title of this thread.   

I opened up a new Brodak .40 and procured an OS FP carb, graciously loaned to me by George Waters. After removing the Brodak venturi and NVA, I took a few cursory measurements and found that the carb would need a very slight modification to fit (I did not want to modify the engine case).   

It took all of 15 minutes to alter the carb and it was a perfect fit.   

I then put it on the test stand and ran it in per the supplied instructions.

After approximately 30 minutes of run-in time, I checked its behavior as a throttled engine. 

I could not have been more pleased with the results. With an 11-5 Top Flite wood, it ran perfectly from around 3,800 to 9,800 RPM, with excellent response anywhere in between. 

So, why did I really do this? To encourage people to get into RC? Nahhhhhhhhhhhhhh - you all know me better than that.

As many of you must have noticed, there is a lot of recent interest in CL scale - all the way from Fun to Precision. Lots of profile planes for this size engine. Many if not all people use three-line systems for engine speed control.

So, why not take one of the most popular CL engines on the market and apply it to use in scale?   

Actually, a great many of the CL flyers also dabble in RC - here is just another alternate powerplant.

Besides, it was fun to tinker!!!!!!

Bob Z.

Hi, Glen - no, because the need for muffler pressure would depend on how it's configured in the aircraft.

Besides, the engine was new and only on a test stand.

Since I have minimal experience with throttle setups, I'm not sure how it would behave at low speed settings.

Bob Z.

I did this a few years ago, but kind of backwards. I had an OS 40 FP that I had changed the timing on the transfer ports, and blocked the boost port. This engine ran a really nice four stroke. I also flew this same engine in a little R/C bipe after adding a carb, and the guys at the R/C field, after hearing it cruise by in a four stroke, wanted to know what four stroke engine it was. They could not believe it when I landed, and they saw it was a two stroke. They had never heard a model engine run that way before. Back when I first started flying R/C pattern comp., we all ran our old non schnuerle engines in a four stroke in level flight, leaning to a two in a climb, just like controline. Late 60's early 70's.