O gauge K Line Napa Valley Wine Train set #K-1511

Sounds to me like there is a possibility that one or more of the wires that go from the motor trucks through the circular holes in the sheet metal frame of the locomotive has been cut. This would be very obvious if the loco runs fine on straight tracks, but then jerks or stops upon hitting a curve.

It is not just K-Line, but when locomotives are manufactured, wires are usually bundled inside the locomotive. But there needs to be enough slack with the wires to allow free swivel movement of the motor truck to the left and right. If there isn't, then over time the plastic covering of the wires can be cut by the sheet metal frame, thus causing a short... leading to what you are describing.

If this is not the case, it could be a lose wire inside the locomotive. But with all the K-Line locos of this sort that I own, I have never encountered that. Though I have had a case or two, of the plastic covering of the wires being sliced by the sheet metal frame.

Should this be the case, you could take a rubber grommet, put a slice in it (like a letter "C, insert the wires inside it and then work it up into the hole of the sheet metal frame. It would probably be advised to also either replace the faulty wire, or cover the break with either electrical tape or shrink tubing.

Also, an unsolicited side note: The Lionel 1033 transformer, using the B-U voltage post setting (0-11 volts) is ideal for running this sort of K-Line locomotive. They will run slowly and the 11 volt max helps limit them flying off the track on curves.

Thanks for the input, I will take a look inside to see what is going on.  Also appreciate the advice on the current limit, these things do want to fly.  

You can also - if you don't have a Lionel 1033 - rewire the motors to series instead of parallel, which is the way they come. Doing this will reduce pulling power, but there are other advantages in addition to eliminating the "jack-rabbit" running. For example, if you have a postwar or MPC caboose with a 12-18 volt bulb, it will hardly look illuminated unless you are running the engine with a long enough train so as to not run it off the track. By re-wiring the engine to series, those illuminated cars will look more illuminated without having to change the bulbs to a lower voltage - which would then be too bright if you then ran them with a say, MPC era locomotive.

For me, I change the bulbs to lower voltage ones, having others with higher voltage ones I can run with the K-Line locos. Or like with something like the aquarium cars... I use the gear driven ones with my K-Line engines. The motor driven aquarium cars are better with a postwar, MPC or modern loco that has a higher voltage operating range.

There have been a good many threads here on doing this re-wiring, if you do a search. Also, sometimes it's easier to search using Google instead of using the forum search. I've used Google a number of times and it takes me to posts that have been made here.

Good luck.