A goal on either side of halftime plus a late red card to Motagua ensured the LA Galaxy kicked off their CCL group stages with a 2-0 win.
Adam Cristman opened the scoring early, lunging to toepoke a low AJ DeLaGarza cross home in the 13th minute.
Playing in the Home Depot Center, the host side kept peppering Motagua's goal with shots, including long-range efforts from Landon Donovan and Mike Magee. Cristman was only prevented from doubling his tally by an exceptional diving save from the goalkeeper.
On the hour mark Donovan made sure of the result by slamming a volley into the upper near corner of the goalmouth after a David Beckham delivery slipped through to him.
The end result moved beyond doubt when former MLS player Ivan Guerrero tried to spear Sean Franklin through the torso with the bottom of his cleats, picking up a red card in the process.