Krusty the Clown over on the JJ has a great tip for cleaning your greasy old parts:
I use an old banquet coffee pot as a hot tank for cyl’s, heads and other small parts. Mix up some simple green and water 50/50 and let’er get hot. It will even remove the old paint on cyl’s. The best part is you can just blow them dry and paint them while their still hot.
In the same thread, there is a link to an old post by Jeb, along the same lines, but with a little more detail:
STEP 1)- Go buy some Yamaha Carb Cleaner. The Part Number is ACC-CARBC-LE-NR, order it online or get it from your local dealer. It smells a little like Simple Green.
For lightly gummed up carbs, you can pour it in your gas 50/50 and run it like STP gas treatment. But that’s not what we’re talking about here. We’re talking about maple syrup in the bowl, we’re talking crusty, powdery, cracked varnish gumming up your action.
STEP 2)- You’re going to boil your carbs, so get something that will hold hot liquid. Get an electric hot plate and a big metal can, get a crock pot, some guys use a drywall mud pan to boil 4 cylinder carbs over a hot plate. I use a Fry Daddy.
STEP 3)- Pull the bowls, top caps and slides from your carbs, put the little pieces in a tuna can and put everything in the container from STEP 2. If you feel like doing a total carb teardown, go for it. I just pull the float, the float needle and the accellerator pump stuff, but I leave the jets alone. Trust me, everything WILL get cleaned out in the soup.
STEP 4)- Mix the carb cleaner 50/50 with WATER, cover the carbs with the mixture, and heat it to a light boil - the surface should barely be rolling. Let them cook about 15 minutes. The old dried up gas is getting melted away. Mmmmmm, petrol soup.
STEP 5)- Rinse the pieces in fresh water, and blow them dry with compressed air. Check the bodies and bowls to make sure all the small passages are clear, and boil them a bit longer if they won’t clear out. BONUS: The outside of your carbs are geting clean too! If you feel like bringing out the shine, spray them down with canned carb cleaner and scrub them with a brush. Let the pieces dry well, and reassemble the carb. That’s it!
1. Do this outdoors, or in a VERY well ventilated area - the fumes are pretty rough.
2. The cleaner will not harm rubber parts-unless they’ve already started deteriorating. It WILL remove paint from painted parts, like black carb bodies. Brass parts left in too long-or at too high a temp-will discolor.
3. The stuff is reusable. After it cools down, pour it into a jug and cap it - it will evaporate quickly if left in an open container. Every once in a while strain it thru a paint filter to get the grunge out.
4. Wear rubber gloves. This stuff will pull the oils out of your skin in no time.
I really like the banquet coffee pot idea since the tank and heating element are together, plus they’re pretty big and you can pick one up on craigslist or a yard sale for super cheap.