Last week I upgraded my machine from a Breville Cafe Express to an E61 machine with a Mazzer SJ grinder. Burning through a fair bit of coffee trying to get things dialed in on the grinder and machine but fortunately the vendor gave me 3 bags of coffee for this very purpose.

Anyway the Breville pretty much made the Espresso for you. Very little thinking involved and even less control over the process.

My question is when timing a shot do you start the timer when you flip the lever or when the first drop of coffee leaves the group head? Watching a video on youtube last night leads me to believe when the first drop leaves the head. But the Vendor when giving me the nickel tour of my machine said when you flip the lever.

My first cup of the day today was
17.5 grams coffee yielding 34 grams liquid in 30 seconds (from first drop)

Which I think is getting me pretty close to where I should be. At least the shot was better than I was getting from the Breville. However I noticed the flow rate was very slow at first, pretty much a drip. If my Yield is accurate and it is starting that slow am I safe in assuming that I am getting channeling causing fast flow in the end? The puck showed no visible signs of it but this is all new to me. Or is this more an indication to keep adjusting grind settings?

Or is the answer to both questions
Yes.

EspressoRide wrote:My question is when timing a shot do you start the timer when you flip the lever or when the first drop of coffee leaves the group head?

For the tl;dr crowd, timing starts when you start the pump. For more previous discussions, try some of the site's forum search tips. For example:

• When do you start to time the shot?
• When is the start of extraction time?
• Timing of extraction starts when?
• Timing a double shot
• What is the correct method for shot timing?
• When to start timing shots from naked portafilter?
• Pour time begins when...

The majority agree the timing starts when the water first makes contact with the coffee, i.e., when the pump starts.

Some espresso machines have extended preinfusion times that may last 8-10 seconds (e.g., E61 with vibratory pump like the Quickmill Anita), others bead almost immediately (e.g., no preinfusion with rotary pump like the Elektra A3/T1). For those with long dwell times, Jim Schulman suggested the convention that timings be reported as half the dwell time before beading. That's as good as any convention, since it's really pointless to worry about 24 seconds versus 26 seconds.

EspressoRide wrote:If my Yield is accurate and it is starting that slow am I safe in assuming that I am getting channeling causing fast flow in the end? The puck showed no visible signs of it but this is all new to me. Or is this more an indication to keep adjusting grind settings?

The timing and brew ratio look reasonable, so stop "chasing numbers" and go by taste. Start with How to Adjust Dose and Grind Setting by Taste. If you want more diagnostic advice, get a bottomless portafilter and post a video.