Hanback Posted February 22, 2016 Share Posted February 22, 2016 I did a lot of gun work this past weekend, and of course, some stuff was far from optimal. So class is back in session. The gun in particular is a very old Classic Army AKM. Lesson one: grease is a necessity for any mechanical system that has component on component physical interaction. It allows the parts to interact with one another without detrimental wear between. Grease is not infinite though, and has a life span. When it reaches the end of its life, it needs replaced, just like on a mower deck, car suspensions, etc. If you don't replace it, it will stop doing its job, and allow increased wear on parts until ultimate failure. So here is a gearbox from a particular AKM that was given to me to diagnose and fix. So imagine driving your car for 150k miles before ever changing the oil, and then attempting to change it. How's that going to go? That is the comparison to this situation. Basically the original factory grease from roughly 2008ish was still in this gearbox, and it had gotten so bad that it began to permanently bond to the gears and shell, as you can see below. Sorry, no good picture of the GB shell. When I remembered to document this I was already halfway through the cleanup of it. Regardless, the grease was so old and caked on that all the parts required a two to three hour soak in break cleaner before then being liberally scrubbed with acetone and chipped away at with a flat head screw driver. I had to finish the shell with a fresh polish with steel wool to get a good surface back after all of this was said and done. The bushing were shot do to all of this as well. All in all, a four hour job between soaking and scrubbing. Now, thankfully the gun still has the original low quality motor and was only run with a 7.4v lipo, otherwise catastrophic gearbox failure from the added stress of the rps with bigger motor and lipo may have occurred. Moral of the story, regular maintenance and lubing with fresh grease with occasional cleaning will save a lot of work and money in the future. I also suggest swapping to good white lithium almost immediately and getting the stock gunk out of the gearbox. Lesson two: The quick fix is not necessarily the best. The stock on this same poor gun had all its screws fully tightened, yet was loose and gave a full +-10 degrees in either direction (side to side movement). The same previous owner and so called "gun tech" tried to fix this by pumping the voids between the stock and inner support with wood glue. Two problems with this: 1, that isn't going to actually solve anything because wood glue is not a filler nor does it do great in compression, and 2, wood glue works great for wood......not metal. Thankfully it at lease didn't take me long to chip away most of the glue from the receiver. The stock took some work with a file though. Once cleaned up, just some simple shims solved the problem, as easy as that. Had some thin, hard plastic sheeting laying around, so I cut strips the size of the stock attachment (sticks out of the back of the receiver, the name escapes me) and placed two on either side. Then I gently slid the stock back on, and hammered it in place before replacing all the screws. Finished product is a perfectly sturdy joint with no give, and its not permanent, so it is all removable if need be. Also, just for laughs, the previous "tech" probably hadn't worked on AK's before, nor paid attention to the breakdown of the gun, because this latch that holds the lower hand-guard in place was not only backwards, it was on the wrong side. Rather than seeing the notch meant for this to be rotated in, the guy put it on the wrong side, rotated it the wrong way, and then taped it down to keep it in place. Made me laugh. Quote Link to comment Share on other sites More sharing options...
Comrade S_Z Posted February 23, 2016 Share Posted February 23, 2016 That baked on grease looks horrible, had a few of those myself on used "parts lot" mechboxes. This is where an ultrasonic cleaner really comes in handy, let them soak for days. Those are JG stock gears, so who knows what type of grease that actually is. I cringe everytime I read "worked good last time I fired it 3 years ago" in a sales ad. 1 Quote Link to comment Share on other sites More sharing options...
Hanback Posted February 24, 2016 Author Share Posted February 24, 2016 This is where an ultrasonic cleaner really comes in handy, let them soak for days. I like that idea, a lot. I use them here at the university for LOX cleaning components and they are effective as heck. Im going to see if I can snag an old one to use from now on. Thank you sir! Quote Link to comment Share on other sites More sharing options...
Bear Posted February 24, 2016 Share Posted February 24, 2016 Small ones can be gotten from Harbor Freight for relatively cheap as well. Conversely, I've been reading up a lot on soaking carburetors in Pine Sol as a method of deep cleaning. I'm considering it as a solution for gunked up gearboxes too. Quote Link to comment Share on other sites More sharing options...
Comrade S_Z Posted February 25, 2016 Share Posted February 25, 2016 PineSol should be fine, might want to double check for petroleum content though. It should work on alloy (aluminum/magnesium) and steel pieces, not sure I'd let polymer parts soak in it. Quote Link to comment Share on other sites More sharing options...
Bear Posted February 25, 2016 Share Posted February 25, 2016 Good call. I know it will swell rubber parts from other user experience. No clue on what it would do to polymer, though I don't think it contains petroleum products. It does have other solvents though. Quote Link to comment Share on other sites More sharing options...
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