Clearly, that oil sheared to well below grade in 2500 miles. I'd guess it contains plenty of the polymers that improve viscosity index and reduce pour point. Motorcycle engines are tough on oils, especially oils that contain polymers.
My suggestion is to try Mobil 1, 20W-50 V-Twin oil and change it at 2000 mile intervals. The M1 is a very robust oil, designed for high temperatures, high loads and it has an excellent HTHS of 5.8 (viscosity at 150 deg C)
But more importantly, Mobil 1, 20W-50 is among the most shear stable of all motorcycle oils, regardless of price. Take a look at page 10, "Results, Viscosity Shear Stability, SAE 50 Group 2" here:
http://americasoil.biz/files/g2156_A_study_of_Motorcycle_Oils.pdf
Also, don't get wrapped around the axle with "viscosity index" numbers for motorcycle oils. VI improvers don't help in motorcycle applications. Unmolested PAO based oils have a VI of about 140. The M1 20W-50 does not contain VI improvers. It's VI of 142 is excellent based on it's formulation.
In other words, your original oil is supposed to behave as a 60 at 100 deg C, yet shears to a 40 (and is probably much worse at 150C) . The M1, is a 50, and will retain it's viscosity.