Wesley Kemboi was the hero for Stima, as his first half double silenced the large Leopards following in Nakuru.
Mike Baraza gave Leopards hope late on, but it was not enough, to effectively throw open the 2012 title race.
Stima took the lead on 16 minutes, Kemboi heading home after a great cross by Alloys Mangi to give the home side the lead at their temporary home.
Afterwards, they looked like adding more, as Leopards were off the pace and all over the place in midfield.
Coach Jan Koops, who was quiet all afternoon made his first piece of movement on the day, a double substitution just before the break, Mike Baraza and Jimmy Bageya for the very poor Charles Okwemba and Laurent Tumba.
Despite the subs, it was Stima who added a second, when a defensive blunder by Leopards keeper Barnabas Tiema and left back Idrissa Rajab handed Kemboi a clean run in goal and he did not need a second invitation, as he made it 2-0 just on the stroke of half time.
Opens up title race
The second half was much better from Leopards, who knew they had to chase the game.
Baraza and Paul Were would have good opportunities to score, but poor first touches let them down.
They would eventually score though as Baraza's weak effort spilled past Stima keeper Ben Roberts Mandela and into the net to make for an interesting last few minutes.
However, with Stima having ten men behind the ball at all times, it was always difficult for Leopards, as they slumped to defeat.
The result means that Leopards lead atop the TPL is just two points above rivals Gor Mahia, with the two team set to meet next weekend in a top of the table cracker.