First, take the tools that you know how to use to do jobs that you know how to do.
Second, make sure your bike is in good repair before you leave. Check bearings, cables, bolts, etc.
Third, check your bike over each morning before you ride. Bolts get loose, bearings start to fail, etc. Better to catcht this stuff while you are still mobile as opposed to broken down by the side of the trail in central Nevada.
Fork seals are pretty easy, but the proper seal driver is mighty heavy. I wouldn't drag it along. Film negative to clean a fork seal can usually get you some more life out of a balky seal. Seals and wipers pack small. I might carry those with the idea that I can find a shop with the equipment but they might not have the parts.
Valve clearance would typically just be a few feeler gages (min and max ... you don't need to know what it is, just that it is within the limits). These would pack small. On a bike you have had a long time and that the valves haven't changed much, I wouldn't bother.
Sprockets are easy (at least on a KTM). I have swapped out front sprockets to change gear ratios as a multi day trip progressed to harder terrain and higher altitudes (less power to use, need lower gearing). A different front sprocket is relatively small and light.
A thread was done on this topic months ago ... I will see if I can find it.
Edit:
Here it is:
http://www.rideforum.net/viewtopic.php?t=313
And another one:
http://www.rideforum.net/viewtopic.php? ... ools#p2743
Other stuff:
clutch cable (my new one will be routed along the existing one with zip ties ... I had to end a ride early in CO and ride back to the cabin with no clutch as my extra cable was at the cabin), perhaps a throttle cable (usually don't fail as often as clutch).
In the second post, Hayden mentions wheel bearings and seals. The bearings can get pretty heavy. First, check to see if NAPA carries the bearings and seals you will need. If so, write down the numbers and don't bother carrying them as most any parts store should be able to get them in a day. Seals aren't a must have item, so I would skip those. Oil filters ... I figured out a common auto replacement for my KTM.
Hayden also mentions a chain breaker. I found a really small one called a "Beaver Tooth". Any chain breaker won't do you any good though unless you also carry a small section of chain (3 or 4 links) and two master clips. BTW, you should carry at least one extra master clip at all times in case you lose the one on your chain. Keep the old one off of the old chain.
Further, you can leave a lot of this rare-use stuff with a friend that isn't going on vacation. If you need one of these rare items, they can overnight ship it to you.