General
The QJ's were Bachmann China's first steam locomotives, the first production run released in September 2001. A fault was present in approximately 100 of these models in relation to the alloy used in the chassis which would overheat and cause the whole engine to sieze up after a very short time. In 2009 a recall was issued and lasted approximately one month where owners were able to send their locomotive back for a complete replacement. I'm unaware if these replacement models featured the same original performance fault, as described below, or were the improved type from the fourth series.

Details
Apart from the lettering, they were both identical in details. The locomotive body is plastic with many of the finer details made from brass and seperately applied; namely smoke deflectors, steps, window visors, ladders, etc. Bachmann have truly made a beautiful looking locomotive.

Performance
The engines are quite heavy, but unfortunately much of the tractive effort is lost from the center driving wheel. This happens to be the geared wheel that makes contact with the worm, and as it's diamater is a fraction smaller than the others, it gives a pretty bad lurching effect, more noticeable in forward, that no amount of running in will cure. Since 2007, a replacement set of driving wheels has been available with the center driver having the correct diameter, but is unfortunately flanged (as featured on the 3rd series QJ release). They are nevertheless very responsive, have fantastic slow starting speeds and close to prototypical mainline speeds. 

Electronics
Electrical pick-up comes from the driving wheels and the tender wheels, which is ferried to the circuit board housed in the tender via wires and then back to the engine to the motor and headlights. Headlights are directional and are 12 volt bulbs. These give off a very nice color, but being bulbs tend to heat up very quickly, something to keep an eye on. Swapping these out for LED's (3mm sunny bright recommended) is a very painful task. For those of you who've attempted disassembling one of these, you will know what I'm talking about.

There is plenty of room inside the tender to accept most HO scale sized decoders. As per standard Bachmann practice, they have an 8 pin socket to accept any NMRA 8 pin decoder. The tender shell is easily removed by putting a few toothpicks between the chassis and the frame, and again on the other side.

Coupler Conversion
As with all of Bachmann's steam locomotives, couplers on the back require a NEM European fit (clip). I recommend Kadee # 17's for these locomotives. The clips don't quite clip in place, but with a sharp hobby blade, a tiny sliver from the front of the coupler box will see they click in nicely (be careful when doing this and take of only a very small amount and more again if needed). I use a #153 (scale sized short-shank w/whisker) for the front coupler.