If you took apart your father's watch when you were a kid, you've probably already done this.  For those who are timid or unsure, here is a tutorial.  I had a problem yesterday in the drivetrain of my Musashi, which my most excellent comrades and I troubleshot to the chain idler coming apart.  It was fixed with an Allen wrench (a "hex key"), but it fulminated doubts about the health of the thing, in spite of it only having 15,000 miles or so on it.  So I took it apart and cleaned and inspected it.  The Moose uses a drive pulley and a return pulley on the same shaft.
 

 
The shaft is just a bolt, removed with a wrench and a 6mm hex key.  The disassembled pulleys are arrayed above.  Keep the outer washer and keeper assembly on the bolt.  As for the pulleys, there is an inside washer for a spacer, the inner idler for the return chain guide, a cylindrical spacer between the pulleys, the drive idler with the cogs in it, and an outer washer-spacer, which may come out stuck to the idler with dirt.
 
The idlers are held together with four stainless cap screws and four nylock hex-nuts.  The nuts go into hexagonal recesses on the pulley flanges, such that two screws can be put in from one side of the assembly. and two from the other side. A 3mm hex key will remove them.  The flanges of both of the idlers appear symmetrical, but they are different for each pulley.  The return idler has a round band between the flanges, which appears to be an old Livestrong bracelet.  This provides the resilient surface for the chain to ride over.  The bearing is in the center recess, an ABEC5 precision bearing.  It appeared to be free and running smoothly.  
 
The drive pulley has a fifteen tooth cog made of hard aluminum.  It is not quite symmetrical, for no obvious reason.  It was obviously worn, with rolled edges at the pressure spots.  The middle has a pair of ABEC7 precision bearings pressed into a carrier ring, which ran freely, but noisily, indicating wear.  The picture shows the cleaning liquid used.  The small chisel or prybar is used to scrape the dirt off the pieces before wiping them with paper towels and cleaner.  The use of the dining room table is counterrecommended.  I ordered a replacement idler from TerraCycle for $50, even though the titanium version is not even twice as much and would save several grams of weight.

Quote from FlyingLaZBoy on Jun 3^rd, 2016, 6:55pm:

 
I'm disappointed there was no fire.....

Quote from TonyWard on Jun 3^rd, 2016, 8:12pm:

 
That was a Q-tip in the pan, not a match...

Epilogue:  I ordered a replacement idler from TerraCycle.  The teeth of the cog are smooth and not turned over, as you would expect--apparently that is a wear mode, perhaps because the idler can't move laterally, as recommended.  I see in my post that I had a 15 tooth cog, so I don't know why I ordered the 14 tooth version, but it should work, anyway.  Hope it's not early onset whatchacallit!