The game was point-for-point in the early going, but Pyrinto went on an 11-2 run to break away to 19-12 lead seven minutes into the game.
However, Jekabpils cut the deficit to three points by the end of the period before catching up and even taking a slight edge at 38-37, as teams went to the locker rooms for the halftime break.
Pyrinto did not allow the visitors from Latvia to enjoy the advantage for long and after a 12-0 run in the third quarter and jumped ahead to a 63-50 lead.
Having scored 31 points in the period, the hosts entered the final ten minutes of play with a 14-point advantage, after Yannick Anzuluni made a basket at the buzzer, marking the end of the third quarter.
With just over three minutes remaining, Jekabpils had cut the deficit to just three points after Troy Barnies’ jump shot to make it 73-76, but Pyrinto replied with an 8-0 spurt.
Although the visitors had closed the gap to 80-84, Pyrinto sealed the win with precision from the free-throw line, making 3-of-4 down the stretch.
Damon Williams ad a game-high 21 points for the Finnish side, while Antero Lehto, Kelvin Lewis and Yannick Anzuluni all chipped in with 14 points each.
Rinalds Sisnins was the top-scorer for Jekabpils with 20 points and six assists, as Pavels Veselovs added a double-double of 17 points and 11 rebounds.