Damn. I guess I’ll try lubricating it with 3-in-1 oil as my friend Todd suggested, but it’s quite likely that I’m going to need to buy new motors.

http://news.lugnet.com/robotics/rcx/legos/?n=3977

I posted this to lugnet.robotics.rcx.legos:

My robot is having a hard time getting around and I think that it’s because the
motors seem to be sticking. Even on my linoleum floor, my little tank robot
often gets stuck and goes in slow circles, because one motor gets stuck. Once I
nudge it or pick the robot up, the motor kicks in again but only for a little
while and then gets stuck again a few seconds later.

I am thinking that the motors need lubrication. Is this a good idea and if so,
what type of lubrication to use? I have WD-40 and Tri-Flow, a teflon-based
lubricant that is used for bikes, skates, etc.

Would either of these work and not damage the motor?

and I got the following response:

You may want to check if your motors are the new type 9V geared motor (#43362).

If so, please be aware it is prone to failure, the first sign being sticking. Pl
see my previous post on this ailment:
http://news.lugnet.com/robotics/?n=24484&t=i&v=a

No amount of lubrication is going to help. In due course the motor will become
permanently stuck and useless. Such is the natural history.

C S Soh