If your Marx train runs slowly, the problem could be a number of things. Fortunately most of them are easy to check and easy to fix yourself.
Check your rolling stock
Frequently the reason a Marx train runs slowly is because of the cars, not the locomotive. Make sure the wheels are all properly snapped into place and the wheels turn freely. Add a drop of oil to the axle on both sides of the wheel, then spin the wheel. You’ll notice it spins much longer after adding some oil. The type of oil you use on your rolling stock isn’t critical. Raid the quart of motor oil you keep in the garage to top off your car if you need to.
If you have any lighted cars with pickup shoes, make sure the pickup shoe doesn’t drag too badly. If it’s correctly aligned and the wheels turn freely, it’s probably OK too.
The Marx design doesn’t lend itself to debris getting wrapped around the axle, but if you find anything wrapped around the axle, take the wheels and axles out, pull that off, and then replace the wheels.
Rusty wheels and axles can also increase drag. Fortunately that’s easy to fix. Apply some oil and then run it. The oil cleans the rust off pretty quickly.
Check your track
If your Marx train runs slowly only on part of your layout, check the track near that spot. It could be a loose pin. Tighten the track around the pin with a pair of needle nose pliers. There’s a pretty good chance that will straighten out the problem.
Also check how dirty your track is. Dirty track conducts electricity poorly. Rusty track conducts electricity even worse. You can clean rust off with a Scotchbrite-type pad. You can clean dirt with a bit of alcohol or mineral spirits and a cloth. I used to use an old sock.
Yes, you read that right. I used to use. You see, I have a trick that lets me get away with not cleaning my track. I haven’t cleaned my track in almost two years.
Check your wiring
If you just ran one set of wires to a lockon connected to your track, there’s a chance that’s causing your train to slow down on the far side of your layout. Add a second lockon on the far side of your track and run a second set of wires back to your transformer. Be sure to wire the second lockon identically to the first so you don’t create a short circuit. Most layouts could benefit from having additional feeder wires. I know one guy who soldered wires to every single track section and ran them back to his transformer. It was a ton of work, but his trains run really smoothly now. Normally, you can get away with a set of wires every 3-4 track sections.
The thickness of the wire you use also matters. 18 gauge wire is the absolute minimum you want to use, and most layouts would benefit from 16 or even 14 gauge. I prefer stranded wire because it’s really hard to troubleshoot a break in solid wire if it ever happens. But using thicker wire and running it to more track sections never hurts.
Clean your locomotive’s driver wheels
I can’t tell you how many times I’ve bought a non-working Marx locomotive and it turned out all I had to do to get it to run was to clean the big driver wheels on it. Something about the metal that Marx used attracts dirt, more so than other makes of trains.
I use cotton swabs and some mineral spirits to scrub down my locomotive wheels. Mineral spirits removes the dirt faster than alcohol. Repeat until the swab doesn’t pick up any additional dirt. You’ll notice the wheels look a bit different when they’re clean. The color changes.
While you’re at it, look at the axles on the underside of the locomotive. If you see anything wrapped around those axles, try to pull it out with some tweezers. On some tough engines, I’ve had to alternate between tweezers and a hobby knife, cutting a bit of the debris, then pulling it out, and repeating. Hair and carpet fibers stuck in between the wheels and bearings can be a big drag on performance.
Clean the motor – the cheater’s method
If you’ve tried all of the above and your Marx train still runs slowly, and you tried a different locomotive and it runs fine, the motor probably needs to be cleaned. Once a motor gets fouled with enough carbon dust, it can run slowly.
The cheater’s way to fix this is to apply one drop of oil on the commutator. And I do mean one drop. Too much oil acts like an insulator, and will result in the locomotive not running at all. But assuming the motor isn’t too far gone, applying one drop is enough to clean off enough carbon dust around the brushes and hold it in suspension to keep the motor from losing too much power. I’ve described this method in more detail here.
Clean the motor – the thorough method
A more permanent fix if your Marx train runs slowly is to take the brushplate off the motor and clean the commutator thoroughly. Don’t worry. It’s easier than it sounds.
Dropping the motor out of a Marx locomotive is usually a matter of removing the two screws on each side of the locomotive, then sliding the motor slightly forward and tilting it down. Then you can proceed with disassembly.
Remove the brushplate by removing the two nuts at the top and the screw at the bottom. Be sure not to lose them. When you lift the brushplate out, be sure not to lose the two carbon brushes. Sometimes they stick inside the plate and sometimes they fall out. Try to keep track of which brush came from which hole.
Clean the carbon dust and other debris off the commutator using cotton swabs and alcohol or mineral spirits. Alcohol is usually good enough, but mineral spirits sometimes makes the job go faster. You should be able to make the commutator shine like a new penny. Most importantly, clean the grooves between the plates with a toothpick. Pick out as much of the debris as you can. Usually it’s carbon dust in between the plates that causes these motors to lose power.
I always wipe the brushes with a paper towel, just in case there’s any oil or anything else on the edges. I also clean inside the wells where the brushes go with a cotton swab. Put the brushes back in the wells, with the grooved part facing the spring.
Putting the plate back on can be tricky. I put a piece of thin cardboard, such as an index card, over the holes to hold the brushes in place while I stick the brushplate in. Once that’s done, I can pull the card out before replacing the screw and the nut. I’ve found this trick helps more than anything else I’ve come up with.
I always test the motor on the track before putting it back in the locomotive.
If you replaced the brushes the way they came, the motor should run really nicely now. If it’s a bit awkward, the brushes probably need to wear in. Sometimes I found I put the brushes back in correctly, but I faced them the wrong direction. You can rotate the brushes with a screwdriver. There are four possible combinations of positions. Try rotating the brushes until you find the combination that makes the motor run best.
If the motor squeaks at all, you need to lubricate it.
Lubricating the motor
Lubricating the motor isn’t rocket science. There’s usually a felt wick at the center of the locomotive. Put a few drops of light oil on the wick. I like Labelle 107. It works well and comes in a handy applicator. If your motor has no felt wick, put a drop or two on the bearing in the same place on your motor.
Flip the motor over and apply a bit of grease to the gears. I like Labelle 106, which contains PTFE. It improves running and reduces wear on the gears, which aren’t being made anymore of course.
Finally, flip the motor so the wheels are facing upward and apply one drop of oil to the axles. The bearings had oil impregnated into them at the factory, but adding a little modern oil doesn’t hurt.
And that should be it. If your Marx train runs slowly, one of these six things will fix it.