RE: Cox Space Bug .049??
Few things in model engines are more complex than keeping track of the variations on Cox cylinder barrels.
To begin, there are three different external shapes. The original, as on your engine and the picture Dickeybird posted, are the same smaller diameter from the lower flange to the bottom fin. Then there is the version with the diameter increased to the size of the mounting flange around the exhaust port, still having a smaller diameter area between the flange and the area around the port. And the third shape with no decreased diameter between the seat and the bottom fin.
And some have flats milled at the top of the barrel for a wrench to remove and install the cylinder.
The exhaust ports can be open, as yours is, or two slits instead of the open pair.
Thus far we have only covered the external appearance, and have 12 possible different barrels. Now we go inside.
To begin, there can be either one or two bypass ports. The "Starter" or "Beginner" engines had a single bypass to limit the power, but most engines had two. But whether one or two ports, they could be milled in one pass, two passes, or three. The milling difference was obvious when the barrel was off, but could not be seen from the outside. The single or double porting could be seen from the outside if it had open exhaust ports, though.
Then we add the bore itself, either 0.401" for the 0.049 or 0.410 for the 0.051. Usually the carb mount on the TeeDee engines was black for the 0.049 and red for the 0.051, but sometimes the colors didn't match. And the reed 05 engines had nothing to differentiate them from the 0.049s.
Then came the latest variations. First was the port timing. All the earlier barrels had "Sub Port Induction," when you moved the piston to TDC there was a gap exposed in the exhaust port, the piston skirt rose to expose a gap allowing a little more fresh air in, the main mixture could be set a little rich, ending up with a bit more power. But it could also let the engine pull exhaust gases back in, and in a tightly cowled installation this was a problem. So there is another version with the exhaust ports raised to prevent the SPI.
The final variation is hard to check, it is the bore shape itself. There's the old standard straight bore, and some late barrels with a tapered bore in the manner of ABC engines. This is intended to have a straight bore when theengine warms up. Seems to work, but these barrels are rare.
Almost 150 possible variations, but I can only be sure of having seen some 25 or so.
Not even mentioned to this point, but some barrels have a number stamped on the side below the exhaust port. These numbers are supposed to identify the variation, but I've seen the same number on different barrels, and identical barrels with different numbers.
One thing that makes it even worse. I have three NIB Coxes, supposedly the same engine, with the same production date stamped on the cardboard in the box, and they have three different cylinder barrels.
You can understand how pleased I was when I finally got a true matching pair of TeeDee 05 RC engines.