This is probably a dumb question, but how much time do the PCs have to stop Sarev getting to the comm tower? It says they have six rounds once he's there, but what about the chase itself?

The map's not much help - it seems to indicate he gets across a ravine in an AT-ST!

I believe (though I don't have the adventure on me) that Sarev's AT-ST starts out at Extreme Range from the Comms Array, so there's your deadline.

Ah, yeah. You're right. That is tucked away in the text. So that means it takes him six successful Maneuvers to get to the bunker: two from extreme to long, two from long to medium and one each from medium to short then close.

He can do that in two rounds, then, with successful Shortcut rolls and taking extra strain to take two maneuvers. Unless I've made a mistake in the calculation somewhere.

Still doesn't explain the ravine (or why he didn't take a speeder bike if speed was so important...).

But thanks.

The ravine is likely more for scenery than anything. And he likely took the AT-ST for style and comfort. He's an Imperial officer. He has to travel properly.

I decided there is a hidden, retractable bridge across ravine, lieutenant may activate and deactivate it remotely at will when he is close. PCs chasing him in AT-ST may have a problem

When running the Beginner adventure, the chase scene was probably the least exciting part. It might have been better if the guy playing Zal hadn't been absent, but probably not.

The thing is, mechanically it seems very hard for the PCs to catch up. Sarev's a fairly good pilot (yellow + 3 green, which is way better than anyone other than Zal). The Speeder bikes have a better Speed score, but that doesn't really translate into catching up - Sarev can easily use a maneuver to move, then let his AT-ST take 2 strain to move again, and then take a shortcut with fairly good odds of success. Basically, Sarev can get to the comm tower in 3 rounds. The speeder bikes only have a strain threshold of 3, and start out with 1 strain due to the hostile speeder bike salvo, so they only get to take one move per turn (unless the driver rolls double advantages), and in the simplified system used their greater speed doesn't give any advantage.

In retrospect, this would have worked a lot better with the chase rules from the core book. Set the chase condition to have the walker reach the tower in three or four rounds. At the top of each round, roll competitive Pilot checks with a difficulty determined by silhouette and speed. The winner gets to either move one range band closer, or one band farther away, plus one band per Speed difference if the winner is faster.