Can't speak for the TT or XT as I haven't owned them. However I did own an electric start/kick start 1985 model KLR600 for a number of years. Rode the thing everywhere. Even did a trip around Tassie 2 up with the wife on the back. Handled reasonably well in the dirt too. Completed a 2 day Sidetrack ride back in 97 which the great late Tony Kirby used to run on an annual basis. That was when the XR400 was the bees knees in the dirt world. I bought mine second hand with 18,000km on it and it was a bit of an oil burner. Aircleaner looked like a lions xmas cake and the piston ring lances were worn as were the rings 
Gave it a rebore and new parts etc and it performed faultlessly from then on until I sold it and bought one of them flash new XR400 things. The design of the aircleaner is poor. It is a flat type that is sandwiched between a metal cassette type holder that then slides into the airbox. Very hard to make sure it is sealed up nicely around the edges. I used to put heaps of grease around the edges just to make sure.
I fitted a 21ltr Acerbis tank which incresed the range no end. However the trade off was it showed up that it needed heavier springs in the forks. Never got around to that though. It also had a trick acentric cam (very works bike) for the drive chain adjustment. You could also use it to lower or lift the ride height in the rear. Engine counter balances smoothed out the vibes making long jaunts more pleasurable. 20km/ltr average most of the time. Had twin radiators and a fan to keep temp as it should be. Fond memories of the bike.
When it came to selecting a new adventure bike in 2004 I ended up buying a KLR650 based on prevoius ownership of the 600. Still have that bike today and it's been everywhere as well. 66,000km and motor has never been apart. looked after the 600 engine should last as well too. The achillies heel of the KLR engine is the balance chain adjuster which is commonly referred to as the "Doohickey". The adjuster can fail as does the torsion spring sending engine into self destruction mode :'( . Eagle Mike in the US supplies a billet version and springs to fix the problem. I checked mine at 24,000kms and the adjuster was still intact but the spring end was broken. All of which is common even with the later model KLR's.Mr Kawasaki should be ashamed 
There is a wealth of info on the KLR. Have a look at sites like KLRWorld.com & KLR650.NET & Adventure Rider. Sieve though the sites and that should answer most of your questions. The 600 is getting on in age now so make sure you do your homework when you find one that may be suitable. Twin cams, water cooled engines etc can be costly if requiring a rebuild. Good luck with it all. Ohh by the way my 04 KLR has plenty of soul. "What you talking about Willis"
sounds like you had plenty of fun with yours, the kick/electric start from stock sounds like a good thing for sure and your explanation of the airbox setup intrigues me as some airbox designs have almost left me throwing tools in frustration haha.
I am familiar with the doohicky issue (seems like a mechanism to keep you servicing the bike at a kawi dealership to me...) & have scoured ADV / the KLR forums over the past year or so but it seems much of the info i'v found is more related to the 650 rather than the 600, the KLR being watercooled with extra parts to fix/fail does put me off a little though I figured it would assist with engine longevity/highway riding
The KLR650 I rode (2000ish? black/red) seemed anemic and choked although gearing/setup/restrictions/ could have something to do with that, I did like the way it rode and the way the engine felt though it just felt like it wasn't quite there (expecting too much possibly or clapped out top end) I wasn't really digging the small half fairing/display either, I didn't have much time with the bike to warm up to it too.
after what your saying about the costs of rebuild i'm wondering how much difference in cost there would be between it and the XT (assuming new top end + some bearings/seals ect)
I figure it probably sounds silly but I can't see myself owning another bike that doesn't have a kickstarter, though I now see both the later model XT and KLR can be retrofitted easily. I can see your point about the practicality of later model bikes but its always been about the feel, ride and experience (like I have some image in my mind of what motorcycling is to me)
I realy appreciate you taking the time to write that post out, lots of good info and things to ponder.
FWIW, ADB rated the KLR well ahead of the XT in the shoot out they did. IIRC, the XT had some benefits on he road, but was much worse on the dirt.
I'd be looking at an early KLR650, TBH.
Interesting, might have to dig the article up and see the specifics on how they felt about each bike. I like the looks of some of the 650's but some of the colour schemes/shapes are waaaay off imo (haha what a fashion princess huh)
I have been riding a 1983 XT600ZL Tenere quite a bit over the last few years.
The main issues that I know of / have experienced are;
Ignition pulse coil failure - reasonable common
Ignition source coil failure - not quite as common
Alternator stator winding failure which causes the reg/rec to fail - reasonably common
Top gear wear/failure - more common with bike that have done a lot of road miles, top gear in mine is was showing a fair bit of wear (hardening deteriation) when I rebuilt the engine in 2010, the gears are not readily available so I left it as it was and have not done about 7000km of hard riding (APC rally, 2 x Tenere Tragic runs) and the only noticable thing is that there is a bit more noise when running in top gear.
There are some tales of cam and rocker arm wear, but I haven't actually never any engines with the problem.
Like all bikes with a linkage rear suspension system, unless it has been owned by some one who cares, the linkage bearings will be stuffed by now. Similarly, the bushes in the front forks will also be worn and need replacing.
All of the XT600's up until about 1990 are all pretty much the same with just a few changes although the post 1984 models have a different ignition system to the 83/84 models.
I did speak with a bloke who was touring on an early XT and he expressed similar concerns about some of the electrical foibles to the point where he was carrying some spare electrical parts with him (doesn't bother me too much), He also spoke of the 5th gear being an overdrive and many end up shot through lugging under ~90kmph. I am intimidated by those twin carbs though.
I do expect that with any bike over 10 years or so that i'd be doing a decent chunk of chassis/engine wrenching with fork seals/linkages/gaskets/washers/manky electrics and bearings ect being a bare minimum.
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Feel like everything points to the early XT or later KLR650 but the larger ergonomics of the KLR and appearance of the early 600 makes me want for one. Whatever bike I end up with the plan is to purchase a second or basketcase for prosperity, I realy just want to ride and wrench on it, not a show piece but regular use. There's info in this thread that I was unable to find searching other forums and sites that are of a huge help to picking the right machine, thanks everyone.
[edit]: just hit post and wow, that's some wall of text haha.
