Like gerard and other…
Most likely, the track is dirty.
But,
My checklist;
1 buy a red lgb track cleaning block. Worth twice what you pay. Thoroughly shine the track. I do not recommend sandpaper. If a rough abrasive is used, you create tiny grooves to collect dirt. My 2 cents….
2. Track joiners: they should be free from micro gunk/grit. A pipe cleaner is a start. Also those little gum cleaning brushes, like a tiny bottle brush, work into the tiniest crevice. Clean out the crud.
Then, If oxidation on the joiner inside, , ie dark colored, this can be cleaned by using liquid soldering flux on the pipe cleaner. Or, liquid metal polish liquid, such as clear silver cleaner. Rinse. This one step, especially after years, should help, a lot. Yes, you will need to disassemble the whole layout and clean. Pita.
If you’re so inclined, i guarantee you that if you choose to convert to rail clamps, operation will improve dramatically, and stay that way.(did this myself).
3. Gently ‘crimp’ or close the now clean joiners for an EVEN like new snug fit, ie slightly closed at both ends. I use a box nosed electrician’s plier that will evenly grasp the entire joiner length. However, Anything will do, just be gentle. If you dont go rail clamps, which i know are expensive, The lgb conductive grease, a pea sized piece, into the now clean tight joiners, greatly reduces micro grit from re-entering.
4. On your locos…clean the track pick up shoes, use your new lgb block to remove any gunk.
5. Clean the backs of the drive wheels where the contact brushes make contack. Over time, these collect the brush graphite resulting in a dark ring. It is easily cleaned using a pipe cleaner soaked in lighter fluid/naptha, or regular metal polish, simichrome, and wiped clean. I do this with the loco upside down and running, using a pipe cleaner or q tip, small bit of rag. Ditto the treads, if needed. Avoid sharp items that may scratch the metal.
Take note of the brushes (and springs that push them out). Make sure all 4 brushes touch the wheel backs.if not, the bush may be excessively worn. (Replace).
When replacing a set of wheels into the gear box, depress the brushes to clear the wheels so they dont break. Also, on steam locos quartering needs to be perfect. (Look up about quartering if you’re unfamiliar). Simply, if quartering is off, the loco will not run smoothly, but repeatedly ‘bind’ and then move freely.
6 clean the area where the axel enters the gear box, per above. Re-lube lightly with light oil.
When i disassemble a loco, i make sure i have time to do it all at once, so i dont forget the process. Remember this…everything fits, without force. You just need to figure out how to re-assemble. Often, on-line has step by step.
Second tip. I have been servicing my locos decades. Yet, sometimes i need to dis-assemble and assemble more than once to get things right. Quartering, reseating of a motor in its cradle (theres a position pin that needs to properly seat[.
Work over a towel to minimize bouncing screws et al. Use correct lubes, ie bachmann, hobbi lube, lgb grease. In any event, plastic compatible. Remove and clean the old grease. I use dish soap or other degreaser, dawn, toothbrush, rinse, dry, re-lube. Btw, check drive rods and gears for grit clinging to old oil. Again, if necessary, de grease, clean, rinse. If you have old lgb locos, btw, often there is a tiny ball bearing, a thrust bearing, at each end of the motor shaft. Dont lose these. Carefully pick them out with a toothpick, clean and relube, press the ball bearing back into the fresh grease.
Sounds complicated, but it really isnt. Just takes patience, and, you should be prepared with the stuff i suggest for servicing. Lgb stuff is designed for relatively easy upkeep.
Typically, say for a stainz or a mogul, a complete overhaul will take me a couple of hours, fwiw.
Once everything is clean and shiny and lubed, things should run great. If you still have stuttering, id suspect that the motor is worn. Sometimes a shot of electrical cleaner onto/into the commutator/brush area in the motor will flush and clean out old brush dust.The solution, more often, unfortunately, is a new motor.
Best of luck.
Its worth the hassle to get your trains running properly. Imho, theres nothing as annoying as a loco that doesn’t run smoothly. Lgb will run slowly and smoothly when conductivity is decent.