I've just tried cleaning my chain and cogs with some really hot water and washing-up liquid. I also used a toothbrush, j-cloth and a non-scratch scourer. After over an hour of some serious elbow grease I could shift some of the outer dirt and muck, but still can't get the base layer of grease off. What can I use to completely strip the grease and muck off the chain?
A degreaser, whether aerosol or not, is an excellent way to remove grease from the chain.
The degreaser will reduce the amount of elbow grease required but be careful and use a set of nitrile gloves to protect your hands.
My simple chain cleaning method is as follows:
Shift into the big ring and little cog, wet the rag with the degreaser
Grip the chain (lower portion, going from big ring to the derailleur) with the rag, focusing on holding firmly onto the outer plates.
Turn the crank putting the chain through the rag. Readjust as necessary as you remove grease and grime from the chain (ie. don't keep rewiping schmutz back onto the chain).
When sufficiently clean, remove the rear wheel from the bike and place it between yourself and a wall (ie. tyre against your stomach/tyre against the wall keeping the wheel propped between yourself and the wall) over a garbage can.
Using a thin screwdriver or a cleaning tool ( http://www.parktool.com/products/detail.asp?cat=4&item=GSC-1 ) clean the grass and grease build up from between the cogs of the cassette/freewheel. Lightly apply degreaser to the brush portion of the tool and scrub at the cogs to free up the grease/grime.
Using a rag, with degreaser on it, insert the edge of the rag between the cogs and 'saw' back and forth with your hands thus spinning the cassette and fully wiping the whole cog. I typically move from top to bottom of the cassette (keep the grime flowing downwards).
Wipe down cassette, hub and any spokes/rim that could have been contaminated. Reinstall the wheel in the bike and one last time wipe down the chain with the degreaser rag.
And typically ... that method suffices for cleaning any of my bikes. The one caveat is that I typically don't let the chain get grease/grime covered and thus this takes about 3-5 minutes max and works really well. The worse your chain, the more you have to do.
You might want to look at your derailleur pulley wheels and using a flat edge against the pulleys as you spin the crank, remove the grease rings from the pulleys.
You might want to pre scrub the chain (similar to how you did the cassette) to loosen the grease/grime on the chain. A tooth brush w/ degreaser or the GSC-1 mentioned above would be sufficient.
Andddd... that's about all I've got for now. There are a plethora of other methods using chain cleaning tools, removal and soaking of the chain and nastier solvents but for the majority this method seems to work fairly well.
I use a degreaser and chain cleaner to get the grime out - usually once a week. It's really surprising how much gunk coats the chain and cassette. I also take the rear wheel off and use a clean rag to get in between the gears to make sure it's all shiny and clear of stuff that will wear out the drivetrain prematurely (I have to replace the drivetrain every year - no point hurrying that expense along...)
My method, which works very well and is fairly quick (although it required initial shopping and drinking some Gatorade):
Edit: this requires having one of those reusable 'gold links' to detach/reattach the chain at will.
You are left with a fresh chain of just metal. Lube it up and go riding!
The first secret is to try to keep your drivetrain as clean as you can. This usually means not applying too much lube. There's no need to drown the chain in lube -- you want it all on the inside of the chain links, not the outside where dirt will stick to it. If your clean drivetrain gets a bit sticky or dirty a wipe over with a degreaser-soaked cloth will often suffice but if you've been riding in the wet you might need to lubricate it again or if it's really dirty give it a proper clean. Here's my method:
All of my chains have SRAM Powerlinks (or the KMC/Connex equivalent) so I can remove them without tools in seconds. Once off the bike I put the chain in a plastic bottle with a little degreaser (I use white spirits, which is quite nasty but reusable -- just pour it back into a bottle and the dirt settles to the bottom) and give it a good shake (aka the Sheldon Shake). I brush off anything stubborn with a toothbrush afterwards then rinse, wipe dry (important to stop rust) and allow to fully air dry. When dry I lay the chain on newspaper and lubricate each link with a couple of drops of oil, allow it to soak in and then wipe any excess off.
Cassette (aka cogs)
I use a stiff brush and degreaser to take most of the dirt off then run a paper towel or cloth soaked in degreaser between the sprockets to get any remaining muck out. I also clean the derailleur jockey wheels.
Once clean and lubed it's a 10-second job to get the chain back on. It sounds like a lot of hassle but it doesn't take long and if you keep your drivetrain clean most of the time it doesn't need doing often. Clean drivetrains also look nice, work better and are easier to live with (oily, dirty exposed bits of bikes have a habit of touching anything and everything).
Actually, many experts now recommend just wiping off dirt from the chain with a wet or oily cloth, possibly using some soapy water.
While degreasers and other solvents will remove oily dirt from the chain surface, they will also remove the lubricant from inside the chain, thus greatly increasing friction and wear. The dirt will typically stay inside, because it is not soluble :-/.
For example, Rohloff (producers of the Speedhub 14-gear hub gear, and of the SLT-99 chain), recommend avoiding solvents when cleaning a chain: http://www.rohloff.de/de/technik/kettentrieb/kettenreinigung/ (only in German, sorry) (English version). They claim that solvents will not be able to remove dirt from inside the chain (where it causes problems), but will stay inside the chain themselves, and later interfere with the operation of the lubricant.
Ultimately, consider that a bicycle chain is really a consumable, as they only last about 1,000-4,000 km (at least with derailleurs). So if your chain is really, really, dirty, consider just bringing forward the next chain change...
Usually I use the tool like this, put your degreaser inside it and of course the chain inside, rotate your crank and it will clean all part of your chain, inside out.
for cog cleaning,
I use a lemon, natural and works very fine; easy to squezze and use it. After I clean the chain I use no oil for the chain, I use a silicone spray or WD40 spray. The benefit is, that this stuff no have an contact with the dirt, only lubricate the chain.