You can pretty much just look at the tread pattern of a tire and judge how good it will be off road vs. on road. The D606's look like they're a good compromise but they're pricey. Also at a minimum size of 120/90 for the D606, they seem to be too beefy for a stock KLX 250. They'll undoubtably rob performance at the lower end of the power spectrum especially on an un-modded bike which is the last thing we need on these bikes. I wouldn't go any bigger than a 110/100 and finding a compromise there is tough for a DOT certified tire. After much research and 'hand wringing' I went with a Bridgestone TW 302 at 4.60 which is a 100/100 equivalent. The tire is fine except in muddy conditions which it probably true for the K270 as the close tread patterns are similar.
I tried a Kenda Trackmaster II first but it wasn't a good street tire compromise as I use the KLX to commute to work. I removed the Trackmaster and put it on my KDX200 and was thrilled with the way the tire hooked up off road.
The tire I really want is backordered everywhere at a 110/100-18 size. It's the Pirelli Scorpion XCMH Dual Sport tire. The tire tread looks like the perfect compromise between street and trail but good luck finding one. http://www.denniskirk.com/jsp/tpl/ti...fCatId=&mmyId=