Hadn't ridden my KLX 250 since Jan this year, just been too busy to get to riding unfortunately.
Anyway, as usual bike wouldn't start after leavi g for about 6 or 7 weeks without starting her up. Did the usual, drained the carb and still wouldn't start!
After cleaning air filter, cleaning out carb, changing spark plug and many hours of trouble shooting found the fuel tap is clogged on the main position. Found this when trying to drain the fuel. Put it into reserve, waited a few seconds to fill up the flat chamber and bam, started in seconds!!

Has anyone else had this problem? Is it a regular thing and should I get the tank cleaned out?

 

My 06 KLX250S had same issue. I bought it from a guy who set it under a tree for 5 years. It's been a project but it makes sense that small area of petcock would evaporate first leaving residue. I also replaced tankside filters. Cheap insurance I think as tank was rusty and used Metal Restore. Very happy with results.