I have a MSR DragonFly and I've never been able to get it to work properly. I just did a full disassembly and checked all the o-rings and cleaned the fuel jet and control tube assembly. The problem I'm having is that the fuel seems to have a lot of gas bubbles in it when it exits the jet, causing the flame to sputter a lot and never really light. I suspect the fuel intake tube inside the fuel bottle may not be fully submerged, but I can't really tell. Why is the stove so sputtery?

SOURCE: I used my MSR reactor

The nozzle on this and other canister stoves can clog. Check the manual to determine how to clean the nozzle.

Hope this helps.

SOURCE: My MSR Pocket Rocket will

Hi, chances are the jet is clogged - I've experienced this myself on the same stove.

I would leave the rubber o ring alone, the chances of the hole there being blocked are slim, it is more likely to be the outlet jet you can see throught the holes on the riser tube under the burner head.
This tube can be unscrewed - you may need to put something through like a pen for leverage. Once you have done this you can remove the tube and you will see the tiny jet in the top of the brass nut on the knurled base of the stove. Then its simply a matter of finding a thin enough wire or pricker to prod araound in the jet. I have a fine wire brush that works well, although I have only had to do it once in several years.
Put it all back together and you should be back to full power - the whole job takes two minutes tops.
The other thing I did was screw the riser tube back hand tight only - this means I can dismantle and clear the jet when camping if required. It doesnt affect performance or safety. I put a strand of the wire in a blob of blu tak in the plastic case the stove comes with - job done! Hope this helps.