Potato/Potato

A Bee is a lower performance sport engine whereas the TD is a high performance version. The crankshaft is more durable on the TD, it's also a rotary engine in which the engine technically is designed to run one direction opposed to the Bee that will run either or. Older Babe Bee Thimble Drome era Bee engines are a single ported cylinder which generally runs around 14k on a 6x3. While a TD will swing a 6x3, it does better with smaller props into the 24K range. So yes, there's a lot of difference in terms of rpm's. While a Babe Bee can utilize a TD cylinder, your going to use so a lot more fuel. You would probably lose close to a minute of run time if not more opposed to the standard run. You also run the risk of doing a few other things such as breaking off the crank pin and or wearing out the extruded case. The other thing is that true TD cylinders are increasingly getting more difficult to obtain and cost usually 3 times the amount of a standard Bee. However, your not going to obtain TD performance from a Babe Bee.

              There's a few things that one can do just to extract more power from a stock  Bee. You can use a high performance plug which was stock on the TD. You can offer a bit more nitro to the engine. Most Bees generally fair well on 15% nitro but even using 35% nitro offers more rpm's but fuel economy also goes down a bit. You can also open the backplate up by drilling out the intake hole a bit but once again fuel economy goes down. Remember, your not making power if your not burning fuel. Therefore, any increase of power means increase in rpm's which equals lower fuel economy.

                Keeping in mind that there was a point that Cox stopped offering different model cylinders and essentially used mostly the newer Sure Start cylinder for all of their engine used in the new line. Even the Babe Bee from the late 80's used dual bypass ports which offered close to Black Widow performance. The Babe Bee as most came to know it was now defunct. The purpose of the original was to provide a easy to run sport engine which could be used for most applications which offered good performance, torque and economy.

          As far as plane size, the Babe Bee on a control line plane flew a 115-130 sq inch of wing  plane sufficiently. A TD can fly a 220 sq inch plane very well. If control line flying is your style, integral type Bees , Black Widow, Golden Bee, Babe Bee have a lot of shortcomings. They're fun, they make us all smile but the reality is that after your flying progresses, you want to take a sledge hammer to them. I have over the past 40+ years figured out many of the problems these engine develop new or old. When I go to fly, I want to fly and not play mechanic all day. When dealing with reed valve engines, it's very easy to suck up small seeds or dirt into these engines. The TD isn't critical to this problem assuming your not sucking in grit.  While some feel that's a part of it, I would rather take my time working on a engine on the bench. I also prefer not dropping small screws, reed valves in the grass at the field trying and then trying to find them which generally results in not finding them.