The tear down (part 1)
The very first thing I learned with a Suzuki GT250 is to loosen the exhaust support bracket (by the footpeg) before attempting to loosen the headpipe.
Sure, it looks like you can just use a big screwdriver and hammer on those nifty exhaust pipe slots to remove the pipe from the exhaust port (as I did with the Yamaha Trial 80); but after 10 minutes of hammering and spinning the exhaust pipe collar, it wasn’t coming off (all with a few choice words). After loosening the support bracket, the pipe came off really easy! I ended up having to have the crank shop re-thread the exhaust port on the left cylinder.
Be sure to take pictures of every nut/bolt/part before you move on – you will thank yourself on reassembly. Also, put each parts section in a disposable cup(s) labeled with a permanent marker with what exactly the parts are for…at the time, you will think, “oh, I’ll remember where this goes,” but you won’t after 50 more nuts/bolts/parts come off.