Tuchanka

Tuchanka has seen better days. War has torn the krogan homeworld apart like a hurricane, leaving a majority of the planet in ruins. The krogan are not friendly to aliens, but when you visit Tuchanka you will be able to help out a few krogan in need.

Combustion Manifold

Reward: XP

The mechanic working by the massive tonka truck fumes at the fact his people expect him to repair a chunk of metallic junk without even the proper equipment! It seems the combustion manifold is required to restore the truck to working order. Building one from scratch would take additional days of labor, and he would greatly appreciate it if you actually had one for him. You will find the combustion manifold during Mordin's loyalty mission. You can still go see the mechanic and turn in the combustion manifold to complete the quest without speaking to him about it prior. Helping him with this favor loosens up his lips a bit and makes him more willing to talk to you.

Killing Pyjaks

Reward: XP, store discount

Ratch is among the only krogan who even give you the time of day, though mostly due to the credits swimming around in your pockets. Credits truly make the world go round. The shopkeeper will give you a discount only if you help him out with a little pyjak problem. Pyjaks resemble little mechanical rodents and can be found infesting the gun range. Step up to the left gun platform to start this mini-game. Basically, pyjaks scurry out and make a break down the field. Your objective is to launch projectiles that explode on impact to kill them. You have only so much ammunition for each round and can allow only so many slip past your death ray before you fail the task. You need to outlast four waves of hungry pyjaks to satisfy Ratch, at which point he graciously gives up the discount.

Additionally, you can purchase pyjak meat here and feed the delicacy to Ratch's pet varren, Urz. Then, you can use Urz to cash in more credits from the pit fighting.

Missing Scout

Reward: XP

When you begin Mordin's loyalty quest and speak to the chief scout, the chief mentions that he sent a scout in to pursue the salarian's captors but communication with the scout has stopped since. If you're heading into Weyrloc territory, you might as well help him out. As you go through Mordin's mission (following the walkthrough, of course), the missing scout eventually turns up, but in a dispirited and rather pitiful state. You have two choices: either leave him to rot away and die, or bolster his spirit to get the krogan running home. It will take a little convincing to get him off his feet, but when he does and you speak to the chief scout afterwards you complete the mission.