Not all cheap, plastic bike parts are junk: at lots of bike forums, people automatically think plastic pedals are non-serviceable and junk. Funny thing is, there seems to be a general consensus on this, and nobody cared to take apart such a pedal!
Most plastic pedals I know of is quite serviceable, and long lived. I bought VP Components VP-536 clone for $12 or less about 2 years ago, and they performed admirably. After 2000 kilometers of heavy use and abuse, I have zero complaints about them. They are not the smoothest running pedals I know, probably due to tiny ball bearings, but they are my go to pedals.
Ok, now lets take them apart, clean, relube and inspect! We don’t need too much tools: a 12mm socket, a 14 one, 17 spanner, few qtips, and of course, a trusty grease.
We need to pry this plastic tap open. You can use a small screwdriver…
Hold the threaded side with the spanner while removing the 12mm nut – note that it’s either reverse threaded or normal threaded, depending on which pedal you work on…
Nut and washer removed. Washer is a bit hard to remove, so use your screwdriver to rock it back and forth. It will loosen and fall off.
Last one…This is a 14mm nut, also the cone. If you don’t have a deep enough socket, squeeze your screwdriver between the nut and plastic casing, and use your spanner on threaded side to loosen it.
Carefully pull the pedal axle. As far as I can remember, there are 14 ball bearings on one side, and 13 on other.
Grease is dried up and looks quite dirty…
Clean the cups with rags, paper towels or qtips. You may need solvents if the grease is very dry.
Clean the pedal axle, and all other parts…
Clean the bearing balls. If they are damaged, replace them. I always keep various size ball bearings and buy them in bulk: they are much cheaper then buying branded stuff.
Grease the cups. Apply liberally. I use NLGI 2 or 3 grade grease. Ball bearings will stick to it…
Balls in place (!)
Grease the axle.
Slowly and carefully insert the axle in place, while holding threaded size of pedal upright. And while holding the axle in its place, insert the ball bearings on other side.
Tighten the cone-like retainer nut. Do not tighten it too much. Pedal shaft should move freely.
Washer in place. Tighten the flat nut over this one, it should be fairly tight.
Apply copious amount of grease, this will act as a dust and water barrier, as the plastic cap looks pretty pathetic to provide a good seal.
That’s it. It takes some time if this is your first time, but if you get used to it, won’t take more than 20 minutes for a set.