The only trailside problems I had on my green DRZ-S were caused by cables. The speedo cable failed in Montana while on the Great Divide Route
I'm not sure what happened; did the speedo mechanism spin? I posted this picture on thumpertalk.com, and did not get a good answer, only flames.
I installed the wheel correctly and always torqued the bolts. Maybe it got caught on a branch?
I removed the cable and rode home without it.
After eating dust for hundreds of miles on this same ride, my throttle tube had so much dust in it that it was very sticky. That was not fun when riding on a narrow, twisty dirt road on the side of a mountain. I cleaned the tube, but had to replace the tube and throttle cable when I got home.
If the bike is stock, case savers are a must
. At a Four Mile Freakout, a rider from Illinois got a rock stuck between his skidplate and side case (without the saver). The rock punched out a quarter-sized hole and dumped all the oil on the trail. He was trucked back to the campsite, where a quarter and JB Weld fixed the hole well enough for him to ride back to Illinois. You don't want this to happen to you.
Pack JB Weld anyway, and flat-packaged duct tape.
Get another clutch cable and route it along side the one already installed. The backup cable can then be easily installed, without removing the tank, when the primary one breaks. Finding a clutch cable in the middle of nowhere is hard. You can also be the hero to a KLR who broke a clutch cable and was stuck north of Walden on a Sunday, when you give him your spare. Who knew that a DRZ cable works on a KLR, if you just route it over the tank?
Check the oil regularly, especially if you ride at highway speeds. Some bikes burn a lot, however, mine used less than 6 oz. of oil during a 2700 mile ride, even with 1200+ miles of highway riding. YMMV. A small can of chain lube is useful.
Make sure you have a socket or wrench to remove the axle nuts. Bring allen wrenches, including a 3 mm for the carb bolts (you did replace those JIS 'Philips' carb screws with allen bolts, right?), and one for the long seat bolts.
An aluminum tube used to prop up the bike to remove a wheel is unstable and dodgy, but useful. Get a good pressure gauge and bring a backup, along with a manual or small 12V electric pump. I added a 'cigarette lighter' socket to my bike to power accessories like this pump - it can also be used in reverse to connect a battery charger when I don't ride the bike.
Bring a selection of nuts and bolts. Just throw them into a bag. I wished I had them when my XR650L lost all the bolts holding down the gas tank, and I had to use duct tape to keep it in place.
Also, you can be the hero to a guy on the trail with a KLX300 that lost the 3 in. bolt that holds the muffler on. I don't know why I had that particular bolt in my toolbag, but he was really happy when I gave it to him.
I bring a few nitrile or latex gloves for repairs. They are small and don't weight anything.
Don't worry about torque specs when doing trailside repairs. You're not bringing a torque wrench with you, are you??