If you look at the weight of the bike, and the 21" wheel in front, I would think 1.8 bar (do not know psi) should be good. On gravel roads I run at 1.2, and offroad 1 bar front and back.
It all depends on the speed and available traction. Too soft at high speed, and the tyre will fold in under the rim. (no fun) Too hard with little traction and the front goes sideways without you. (No fun either)
If you look at how your tyre wears, you should see if you are running the correct pressure for daily use. If it only wears in the centre, then too hard. If it only wears on the sides, then too soft.(unless you take corners like SBK) Unfortunately you only find out about the wrong wear pattern after the tyres has worn.
Maybe Le Cap can help, as he has quite a few KLRs with the same wheel sizes.
hope that helps
If its stupid, but it works, it aint stupid.