I have a new technique that I use to clean my hot ends. It's worked perfectly for 6-months now and I've had no jams or residual filament issues.
This works best with nylon filament (because it has some lubricity) but it's still useful with any type. When I say "works best with nylon" what I mean is if you are printing with ABS, PLA or anything else and you want to clean the head, do it with a short piece of nylon filament.
Steps:
1. Extrude 10mm and then pull your ABS or whatever out at working temp (say it's 230C).
2. Insert a piece of nylon to in and extrude manually until you see it start to come out.
3. Cut the hotend temp to 130C and let it settle. Once there let it sit for a couple of minutes at that temp.
4. Very, very slowly, back the nylon out. I mean like 1mm/second or slower. If you go too fast you'll separate it inside and not get the whole tip. Once you do it a few times you'll get the feel. Once you've moved it about 10mm you are good to pull it out faster.
What comes out is a nylon plug with the shape of the inside of the hot end and a little tip where it was sticking out of the orifice. Stuck to the outside of the filament is whatever else was in there. Do the steps two or three times if necessary to get it perfectly clean inside. No dismantling or chemicals are needed. It's great for clearing jams too.
Here's a shot of one of my cleaning sessions. The left-hand one was first. The right hand one is now clean and perfect:
http://3dprintboard.com/attachment.p...tid=4538&stc=1