Lionel 746/736 Engine Service Recommendations

I would remove the brush plate, to access the armature face.  If you aren’t sure of the last service, it is highly recommended.  I resurface the copper segment of armature with 1000-1200 grit emery paper. I clean out the brush holders with 91% Isopropyl Alcohol, (from any drug store), or Naptha.  Put new brushes in plate.  If the motor is removed from the frame, I would clean the geared end of the armature, with an old toothbrush, and a solvent (alcohol/Naptha) and relubricate the gear. As far as the hole, I typically use a lightweight oil, just to keep the inner shaft lubricated.  These-turbine motors are pretty bullet proof, if maintained regularly.  Good luck

Do I fill the hole all the way up til it’s fillign the hole? Or just put in a few drops?

I would only add a few drops of oil, say 4-5 drops should be sufficient.  Where the geared end meshes with the drive gear needs to be cleaned out of any old lube, and re lube with newer lubricants.  

Six or seven drops should be good enough. If you remove the brush holder you might as well remove the armature and clean & repack the ball bearings. You may have to gently rotate the armature to get the worm through the bushings. I use Labelle 106 grease for the bearing/races and a drop or two of light oil once assembled (don't forget the oilite bushings). You also need to check the grease in the gear well. I just serviced a 746 and the gear grease was like molasses. 

two things to be careful with when you pull out/apart any motor of that style...berk, turbine, or J...first, when you take the two screws out that retain the motor,watch for any added shims that may or may not have been added to correct gear mesh, they can stick to the bottom of the motor, and easily get knocked off, or they can stay in the chassis and fall off if you turn the chassis upside down. usually, if there are shims, they sit over the  alignment pins, and are just tiny thin washers. keep track of where they were. Second, if you plan on removing the armature shaft from the motor block, do so over a cookie sheet, or something similar. the ball bearings should be retained in a washer, however they don't always stay put...keep track of how the thrust washer and bearings get stacked for re-assembly. I like to pop the retaining clip off aiming it into a white towel I have just incase it decides to go flying....couple tips I use...