Disassembled portafilter & now my shots are not calibrated properly.

I can confirm the large spring must NOT be around the needle valve but on "top" of the flapper when you reassemble. Another suggestion: clean off the screw threads before you reassemble. They should spin-in easily.

If your cranking on the screws - something is wrong.

This is a great answer, and the picture goes a long way to show how actually simple and straightforward it is to keep the portafilter clean, instead of the widespread fearmongering and dire warnings that abound most everywhere else online! Two Thumbs Up, Henry H!

Going further, lifting the spring shown in the picture will also lift the needle valve on its hinge (don't worry, it won't fall off, just lift the spring and put it aside, it'll slip right back on no problems). This exposes the valve seat for cleaning and it's then just a matter of using a toothbrush, some Q-tips and a household degreaser such as ammonia (caution, it's fairly corrosive, use dishwashing gloves) or glass cleaner to remove the gunk that may have made the mechanism stick in a partially closed position.

When you do that, just be careful not to do it too forcefully, notice on the picture the little feather spring, how it should be set in, should it come off. I simply put my finger on it while I work with the toothbrush so it won't. In any case, it's very easy to put back on but it's a small part to look for should it fly off ;)

Cleaning the outlet spouts in the handle is just as deceptively simple, also remove the handle end cap to clean the inside of the handle, it's hollow and this is where the pressure release goes in case of need, it may be full of coffee residue as well, just imagine what ugly after taste it could give your coffee...

Total actual cleaning time, not counting soaking (I suggest you let it soak an hour in pure household ammonia in a covered container to soften the gunk), was about 30 minutes, including reassembly and running clear water through it from the machine.

Now brew yourself a fresh coffee and taste the best coffee you've had in a long time, possibly not since the machine was new ;)

What picture?

Great question and post. I ruined my first portafilter trying to fix it myself without looking up instructions. Couldn't figure out how to get the parts to work properly. Thanks Henry for explaining in detail what to do. I was so afraid to take apart my current portafilter because of all the warnings I've read online. Your answer gave me the courage to take my portafilter apart and clean out all the crud that had accumulated over the last two years. No wonder my latte's haven't tasted good in awhile. I'm happy to say that after following your step by step instructions, my lattes are better than ever. Thanks again!!

Help. I think I have everything correct on putting my portafilter back together EXCEPT: on large c-shaped metal wire/ring with on end looped and the other bent up. Where did that come from??