Unlikely its any problem with the espresso machine but you might want to check the HB forums on how to adjust the opv to get the correct pressure. If you don't have a pressure gauge portafilter or a scace, you could use the back flush method. This is quite leh cheh and pretty much an estimate. Need to measure how much water is ejected back into the bypass return hose in a set period of time to estimate the pressure.
what grinder do you use? its unusual a finer grind makes the espresso gush out.
May I suggest these parameters as a starting point.
1. Use stock baskets. VSTs need a bit more skill and grinder with micro adjustment.
2. bottomless portafilter if possible to rule prep errors.
3. 15g of coffee in the stock basket. (really need to measure accurately). Weight the filter basket and tare the scale. Use a 0.1g scale.
4. Use a espresso style roast. Light roasts can be funky and not easy to pull. liberty, strangers reunion, dutch colony, highlander, toby, bettr barista espresso blends are ok. I find traditional espresso roasts pull well with lower doses. Light roasted stuff generally needs higher doses on vst baskets. Counter intuitive...i know...
5. since silvia has no preinfusion, the shot should take 30 secs +- 5 secs, from the time you press the switch to the time you off the switch. 14g of coffee should get u a 28g shot for a normale or if you prefer a ristresso aim for a 21g shot.
6. for e61 i usually go for 35 secs. for cremina i go for 40 secs with light roasts and long preinfusion.
good luck!
