Too frothy. Over carbonation?

[marlin]

Firstly apologies if this subject has been covered before but I could not find any answers elsewhere. I'm new to the brewing hobby and my first 2 attempts with single (1.6kg) can extract and a bag of sugar worked well. Then the last couple of kits where with twin cans (no sugar) fermented for about 2 weeks in the same FV, then transferred into a King Keg with 80 g of sugar.
I don't know if its a coincidence but only the twin can kits over carbonated.
My questions are, what are the causes of over carbonation. Could the fault be in the process I used or a matter of sanitation?
I know there isn't one single solution but if someone could point me in the right direction it would be much appreciated

[OldSpeckledBadger]

You might have kegged before primary fermentation was finished. Did you wait until you got a stable FG reading two days running?

[mickhew]

My thought too about the hydro. Also, do you mean the beer is too fizzy? or, you get lots of head when you first start pouring ? if the latter all the kits I've done have been like this, despite getting the correct hydro reading.

[joel_m]

I've only done two kits so far and have had the same with both of them. One in a budget keg the other in a King keg with a top tap (which has been slightly worse of the two).
I found the best way to stop the massive head and put the fizz in to the beer instead was to leave them outside for a few nights after the priming fermentation. When the temperature really drops I guess more of the CO2 pressurising it dissolves (thinking back to my chemical engineering days I'm sure this is something to do with vapour pressure equilibrium...) But I'm sure someone here will be able to give you a correct answer.

Hope this helps!