What do I need to change, I'm still getting some bitterness and extraction times don't seem to be right.

Below are the two scenarios I seem to get most often.

1. I adjust the grind so I get 2oz in 25 seconds but it blondes after 15.
2. I go finer and it takes over 10 seconds before any drips and takes over 30 seconds to get 1.5oz and again it seems to blonde after 15-20 seconds.

Tamping pressure seems to make no difference.

Clean out your grinder if possible (certainly a possible issue of a wider range of particles sizes - ie. small + big instead of all medium etc).

This would cause the extraction pattern you describe, as well as not tamping it toooo hard, and instead dosing a little less if necessary to ensure the coffee doesnt touch the filterscreen when you insert the portafilter into the group head.


summary)
Double check the grind quality, clean out grinder & burrs.
Tamp medium, and level - try applying only a single smooth tamp to avoid compaction of the grinds into more than 1 density layer, followed by a gently polishing.
Reduce the dose if the coffee is too close to the showerscreen (handy test is resting a small nickel/penny on the coffee centre prior to insertion and removing to check for visual cracks on the coffee surface)

Also, it goes without saying that hopefully your coffee is between 5 & 15 days post-roast for judging this most accurately.

Are you using a stepped grinder, like a Gaggia MDF?

Too slow or too ristretto a shot will lead to a dull bitterness; too high a dose can lead to a cutting astringent bitterness. Buy a 1/10 gram scale on Ebay, and polish your technique by dosing shots the same way. If you do, and if you stay around 14 grams, the grinder steps will work.

When you are using base level equipment, a Gaggia or Silvia machine, an MCF or Rocky grinder, I cannot reiterate this point often enough -- Italian espresso gear is designed for 7 gram singles and 14 grams doubles. The top end gear works well at higher doses, the mid level gear sometimes works, and the low level gear you are using almost never does. So you can either spend the next three years pulling Yemen and Harar, or train by making 14 gram shots. Then, all of sudden, all the temperature, pressure, grinder step, and distribution problems will magically go away, and you'll be able to pull shots from most any espresso blend or SO.

Premature blonding can be caused by poor distribution (channeling, etc). Due to the lack of preinfusion on the Classic it is essential that you master even distribution. Are you using a naked portafilter? If not, you might want to pick one up as it will make it easier to diagnose extraction problems. Have you tried WDT? When I was starting out I found WDT made a huge difference especially when I was using a Baratza Virtuoso.

Assuming proper technique, it could be a symptom of past its prime coffee (how fresh is your coffee?) or a grinder upgrade opportunity, but more often it is an issue on the handle side of the portafilter.

Thanks all, here is some more info

1. Grinder is an Iberital MC2 and is brand new.

2. Coffee is fresh

3. I can sometimes see holes on top of the puck which I assume is channeling even though I break up any lumps and distribute evenly, tamper is the cheap plastic one thats way too small

4. Normally the puck comes out feeling dry but now its very soggy. Not sure what would cause this.

It's important when you're measuring the time that your shots run to not include anything after it's gone blond. So, if you get 2oz in 25 seconds, but it went blond after 15 seconds, what you should've done is stop the shot as soon as it went blond (or ideally just before). There's no point in hitting some "ideal" target volume and time if you're filling your cup up with dishwater.

So, you can't get your shots to go longer then 15 seconds?

My first thought is the beans. Just because the roaster say's the fresh doesn't mean they are, and just because they're fresh, doesn't mean they're good. best bet is to order some fresh beans from one of the List of our favorite Roasters. At the very least people will have experience with that bean and will have some idea how it pulls and what it tastes like.

My second thought is that you're getting channeling. This is largely a trial and error process to fix. Start with 14 grams of coffee, and practice tamping lightly, evenly and simply - that's an important part, I've wrecked so many shots by trying to get fancy with the tamping. If that doesn't work, start trying things until something works for you (that's the trial and error part). A naked portafilter is a big help here, to see if and what kinds of channeling you're getting.

My third (and final) thought is to taste the coffee (just the first good looking 15 seconds, not the bathwater). If it tastes good, then at least you've got something to drink while you're figuring out how to get the "right" volume in the "right" amount of time.

The beans were from Has Bean and I've been really unimpressed, I bought the espresso blend and the Sulawesi, the first tasted very thin the latter very sour. Haven't had a drinkable cup

This morning I tried the WDT method and it still didn't taste nice but I didn't get any channeling, haven't got a scale accurate enough to check the dosing however I dosed a little higher and that solved the soggy puck problem.

I was getting better results with the Happy Donkey beans, although far from perfect at least you could drink it.