Greetings Thomas,
Sidestand and clutch switches are horrendously unreliable on any machine taken off tarmac. Don't get me wrong they are fine as safety items in their own right but just add to the complexity in an adverse environment. Mine are both disconnected and the ends double sealed in heat shrink wrap, held against the frame out of harms way by a plastic cable tie.
The fuel level switch and wiring should cause the problem that you are having. The fuel level warning light leads had already been cut off from the switch on my bike so I bought a replacement tap without switch, but more useful to my mind, with a reserve facility plus filter from Steve Goode Motorcycles; 01938 850544
http://www.stevegoodemotorcycles.co.uk Mention my name and he may remember the one he sent me, alternatively measure the distance between bolt centres and the pipe outlet diameter. I wouldn't trust a light as they are so unreliable.
If you suspect petrol starvation through possible dirt from the bike having stood for so long then fit an extra line filter into the petrol pipe, remember that they work in one direction only so check for an identification arrow on the filter body. I do not have one on mine, simply rely on the tap filter. I think that the tank vents through the filler cap as I could not find any other breather system.
Does the engine restart immediately after you come to rest? Or does it require cranking?
Another 'characteristic' of the Suzuki power unit is wear to the thrust washers on either side of the clutch basket. If the washers wear, and it is only slightly, then the clutch does not fully disengage and you can have problems engaging gear from neutral or neutral from gear when the bike comes to a stop.nIt is a really easy job and one that I would recommend even if the mileage is low. The only 'special' tool required is a clutch holder but a universal grip type is suitable and they are cheap enough to buy if you don't have access to one.
I made a PowerPoint presentation about the clutch thrust washer change but it is too large for the Forum to handle, if you want a copy then send me your personal email address and I will send you a copy. (If anybody else reading would like a copy you too or if somebody has a method of reducing the file size).
Now you have plenty to check so put the computer down and get your spanners to work.
TTFN
Hugh.