The first step is to remove the lock cylinder from the latch assembly. With a pick or small screwdriver push the spring loaded tab into the cylinder releasing it from the latch.
Here are the two lock cylinders, old on the left. Note the broken catch on the old one. This is the part that engages the latch preventing the handle from opening when locked.
Now, using a small screwdriver, carefully pull the lock pins out of the cylinder one by one. The little bump on the left side of the lock pin fits into a detent in the cylinder so some (slight) force is needed. Keep an eye on the springs as the have a nasty habit of popping out and dissapearing. As you remove the pins lay them out in the EXACT order that they go in the cylinder.
Now you want to put the lock pins from the old lock and install them in the new lock. One by one insert the old pins in the new lock cylinder making sure they are in the exact same order that they came out of the old one. Make sure the spring is in the right place and push the pin in until it pops into the detent. When you are all done put the key into the cylinder. It should look like this:
With the key in the lock all the pins should be flush with the cylinder with the exception of the very last pin which is the retainer that holds the cylinder into the latch.
If it looks like this, with the pins all uneven, do not pass go, do not collect your $200:
All that’s left is to slide the cylinder into the latch, check to make sure the key works, hang the bag on the bike and HIT THE ROAD, GO ON A TRIP, RIDE THAT THING!
It’s really pretty simple and a whole lot better than carrying two sets of keys for your bags.