I have repaired a few K4's that waddled like you describe.

Look closely at the drive wheels. The wheel itself is metal while the black spokes are a plastic insert; like a hubcap.

The 'hubcap' expands over time and bulges out; interfering with the siderods.

The fix is to cut out the 'hubcap' with a sharp knife and then paint the metal spokes that are left, flat black.

Do you believe just an armature would solve the problem?

I have armatures.

Nice story, thanks for sharing.

Fully seating the connectors would be best but it is generally only low voltage present so if you take normal care you should be safe.

Running wire under anything is not a great idea. But once again let common sense prevail. Is it possible to route the wire so that it is not under your table cover?

When you were cleaning and lubing, did you notice any signs of cracks in the gearing?

What comes to mind for me is the poor solder joints on that era of loco. Check to see it a wire came off at the side of one of the trucks.

Part sent today.

If the springs will not slide out they have probably gotten hot and melted into the plastic.

Dig them out. clean the hole with a file and replace the springs.

It turns out that I had a diagram for BLI and Intermountain.

So can't help you.

John, I have a diagram in my train room. I will look at it and post here later.

I got the diagram and even was smart enough to print it out. Will make one today, Lord willing.

When you say vintage I immediately think of the 80's version. There is no switch to turn the smoke off.

These had a very simple smoke generator that is a little plastic cup stuck in between the frame halves with two wires. One sticks out each side and makes friction contact with the two frame parts.

If the smoke unit still works it's easy to take the shell off and slide the smoke unit straight up and out; which is a good idea because if it still is heating they can get fairly hot and distort the shell where the smokestack come out. Melted stacks are very common.

The cheap Harbor Freight calipers work fine for this purpose.

I asked on another forum for some measurements too but no one has spoken up yet.

I'll check in here to see if you can get measurements. Or you can PM me too.

I could make you one if I knew a bit more about the dimensions. It looks to be 12mm long?