Picked up a used Oscar 2 and picked up the 9 bar OPV kit and immediately installed it.

I did some test shots and it seems it is struggling to keep consistent water flow.

that isn't an OPV issue. it's an issue with the actual design of the oscar 2. You cant run the pump for too long without the pressure from a basket filled with coffee or a blind basket. Basically the heat exchanger chamber (small boiler inside the actual boiler) empties out faster than the pump can fill it. To fill the HX chamber, run the pump with a blind basket until you hear a change in tone of the pump.

2 solutions for this:

1.) never run the pump for more than 3 sec without coffee/blind basket
2.) install a 0.6 synesso ruby restrictor and remove the 0.7 restrictor near the actual pump. just turn captions on http://www.youtube.com/watch?v=qLpv_CvAPPQ

The stock flow restrictor is about 0.9mm, which is too much for espresso, swap out for a 0.5-0.6mm one and your oscar ii will be good to go, there are two way to install the flow restrictor, one is with the OPV, if you are able to find any after markets part, other way is buy a Nuova Appia II 0.5mm flow restrictor, this restrictor was at the end of the pipe that goes to the group heads like a lot of other brand machines, La Marzocco linea mini.

Oscar ii comes with flood like flow rate and that's the issue.囧

Hi
I have not had too much of an issue like this in a while except when I leave the machine for a long time, or if the screen needs cleaning. I rarely have the issue of a lot of steam as in the video. To reinforce an earlier post, I read that the pressure and flow cannot be judged visually as the coffee or blank filter basket is expected to contribute to the final system pressure.

My coffees are less consistent that I would expect from this machine however. I do not think the inconsistency is the grinder or my prep, though I did just purchase a DS64 in case it's the grinder. I also installed the OPV kit from Elektros and set it to 9 bar,

Have you installed one of these flow restrictors, or multiple per the Russian guys' video? I'd really like to know if it makes a difference in getting a consistent flow from shot to shot. Can you let us know more about the mods you have done?

thanks!

Hi again
I'm going to install the new giglers but the nuts on the copper pipe are stuck. I assume they used red loktite or something to make sure noone unlocked the nuts. I do not have a torch to heat the nuts. Any suggestions? Could I just turn on the machine and let it heat up (and be very careful)?