Lionel 623 jerky operation.

Clean the commutator, check the brushes(length, condition, oil soaked?) and brush tension. Also, the motor and power truck appear to be in need of dis-assembly, cleaning, & lubrication.

Make sure you have the thrust bearings and thrust washers in proper order. On the armature side you should have a thrust washer then a bearing then another thrust waher. On the geared end you need a thrust washer a bearing and a retaining ring. Make sure all bearings are present on the thrust bearing ring.

If cleaning the motor does not help, I would look to see whether the backs of the power truck wheels are rubbing against the truck block or magnets when you go forward.
It is a somewhat common problem.

Less common is the drive gear rubbing against the sides of the groove where it sits in the center of the truck block.

If a full service doesn't help the problem, pull the motor out of the power truck, and turn the wheels, to see if there is a "catch" in the smooth rotation of the wheels. Further, the motor could have a loose field assembly, where the rivets hold the field to the motor base. Repair hints are in the Greenberg book. Let us know what you find. 

I finally watched the video. I stand by my earlier comment about wheels rubbing, but I have to say that your engine doesn't run properly in reverse either. While it is not as bad as it is in the forward direction, it is rather jerky in reverse too.

Those engines and their 2023 style Alco brothers should run very smoothly in both directions.

There should be four thrust washers on the motor. LennyJ listed three.

It should be washer, ball bearing ring, washer on both sides of the lower bearing.

Here is the service manual page for the common variation of the motor.

The early version of the motor in this engine does not use ball bearing rings (681-121).

The early version has individual, loose ball bearings.

Hi PennLine and Folks,

      I had a similar operating issue with my old GE 44 Ton switcher.  I don't know if the chassis is the same, but I had to tighten the frame on the powered truck around the black plastic spacer. 

I used clips made from women's "bobbie pins" and super glued them in place with a version of the glue made for oily surfaces. (Also glued the black plastic piece to the metal.)  Although it looks sloppy (I was generous with the glue), it has been working well for 5 years now. I had lost the ball bearing that rests on the plastic piece, and forum member "rlplionel" noticed the missing bearing and then supplied me with a few.

    Hope this helps!

Take care, Joe.

Joe Rampolla's locomotive is a later diesel with a very different motor truck.

I am very fond of those postwar 44 ton diesels.

Joe, which superglue is made for oily surfaces?

Hi Sulafool,

     http://www.supergluecorp.com/s...ue/future-glue-brush
  

     I cleaned the chassis surfaces well then roughed them up with an emery board before gluing.  There is a plastic film on the bobby pins that needs to be scraped off first, also.

     Hope this helps!

     Take care, Joe.

thanx joe!

I, too like the 200 series Alcos and switchers, as well as the 44 tonners. Good idea with the bobby pins. 

Hi Folks,

   When bending the bobby pins, because the metal is thin and brittle, the bend needs to be a rounded corner, not a sharp bend.  I got the idea from the old American Flyer S gauge track clips you used with the Flyer trestles.

    My father loved that locomotive!

    Merry Christmas, Everyone!

Take care, Joe

It was the power truck, when I opened it up there was 60 years worth of black grease and who knows what else.  I felt like a real diesel mechanic at the end of it, well at least my hands did they were so caked with grime.  She now runs like a Swiss watch, one of my best performing locos now.  Thanks for all the help I thought it was an electrical problem and I wasn't even close, it was all mechanical. 

Tinsel chunks from the 1950's, fur samples from long-dead family pets, Berber carpet fibers & cigarette smoke residue from the 1960's, shag carpet fibers from the 1970's, hardened Lionel grease applied in the 1980's, cobwebs and insect fragments from storage in the 1990's, and on and on...