I stopped my Beta from leaking fuel by puting a fuel filter on it. It has only started that leading when on the kickstand a very few times since adding the fuel filter. When it does I turn off the gas and run it dry then turn the gas back on and no leak. I think that carb is is very sensitive to dirt getting in the float needle.
Mine came with 27.5/145 jetting. Going to a 30 pilot made a huge difference in the way it runs. I live at 2,000ft and our club has property at 6,000ft. I think it runs great at both altitudes. Never even had the plug out of it. Best behaved 2T I have ever owned.
Never considered dropping the main to 135. Would that be too lean at 2,000ft?
2011 690 Enduro R
2013 Beta Evo
07 450 EXC