Guys, RMT obviously used a different spec motor in the BANG engines. All my similar looking K-Line engines run fine using a 1033 with the B-U voltage setting of 0-11 volts to the track... no rewiring. The RMT BANG at full throttle on the B-U setting just crawls: It needs the higher A-U voltage post settings.
I believe RMT did this on purpose to make the loco operate better with the typical postwar Lionel transformer with the minimal 6 volts to the track. This engine DOES run SLOWLY without having to rewire the motors. And it's not the circuit board: I pulled one out and wired the loco to run on DC with the same results... the motors need more current than do the previous ones on the K-Line version. And I had a bunch made during different production runs, and the RMT S-4's all behave the same: They need more current to get moving.
The K-Line S-2 was the most expensive of the original traditional locomotives to manufacture because of all the multiple sheet metal folds. It's ironic that RMT must have made it more costly, though surely an improvement with the added sheet metal to the front and rear of the loco.
My biggest grumble with the RMT S-4 is the stiff couplers. Yes, they are die-cast versus the previous K-Line plastic. I believe RMT used a Williams design: They're longer in length and don't swing well, so they have a tendency to derail anything but a heavier car right behind the loco on 027 curves.
Yes, as said above, the horn is a basic electronic blurp, but the added directional LED lights and the strobe light on the cab are a nice addition. For being a lightweight engine, it has very good pulling power. And not to be overlooked, it looks right at home on a smaller layout with 027 curves pulling 027 or traditional types of rolling stock.
It's a tad ironic that this engine has become one of the most difficult traditionally sized engines to find. Both the BEEP and the BUDDY are much easier found. The BANG's are obviously out there, but very seldom do they turn up on the auction sites. Nor do dealers I check have them listed. And when they do, the prices are way above what they were originally selling for when first introduced. Maybe the traditional market hasn't dried up as much as some assume it has.