So..... I've just returned from my trip to Morocco with my XTZ750 Super Tenere of witch I only had 1 minor problem half way through the 2 week trip with dirt in the fuel, solved at the time with new fuel filter and quick carb strip down. Rest of the trip was fine.
The bike has been sitting for 2 weeks in my workshop at home untouched since my return. Today I thought I better give her a run by taking her to work and struggled to start, turning over sounded normal until the battery started getting weak. So I had to hop on my trusty XT600e to get me to work as I have been since my return.
So when I get home I thinks I better give the battery a boost and run the XTZ to ensure I can take it in the morning, so I do so. It tried to fire straight away but as it did the exhaust puffed out a little black smoke and the sound of the engine turning over suddenly sped up, almost sounding like there is a lot less friction. Also I can now feel a vacuum when I put my hand over the end of the exhaust and has not shown any sign of firing since.
Now im going to pull the bike apart anyway as its due a bloody good service etc, but I wouldn't mind a head start on identifying this problem.
I online about carbon build up and valves not closing, but this was on a Triumph forum.
Any Ideas?

I would start with a compression test.

That's the first thing that sprung to my mind. Im thinking valves not seating properly may be the fault. A guy on Facebook Super Tenere group thinks it could be the carbs, the float valve sticking open. But im not buying it. Doesn't explain the change of sound when cranking.

I'd look at the carbs anyway. You had problems with them before, and noone has ever complained about clean carbs, so your time isnt lost, even if its not the problem

Well she seems to have fixed herself! Just tried starting her and she fired up like nothing happened. So I took it out for a blast on the trails for a couple of hours and has been fine since. Ive taken it to bits anyway, give everything a clean and service..
It seems a sensitive bike, but it was very neglected by the previous owner and has taken some time to get to the point of even leaving the country with.
Thanks for your imput guys.