There are two ground connections near the starter and both are suspect. One is direct to the battery and I think the other is to the ECU.
here you can see one above the starter and one below. The lower one goes to the battery. Remember that the - side of the battery is on the right so that ground cable is going from high right side of the bike to low left, it's a fairly long run and the cable is not very thick. Add to that the fact that the stud is only 6mm. Not a great situation.
A solution is to move both grounds to better connections. Here's a photo of the new battery ground.
I am using a bolt that secures the transmission to the block, on the right side of the engine. Not only is it a larger bolt, it's much easier to check for corrosion.
For the other ground (ECU?) I moved that to one of the starter bolts.
Once again, larger bolt and easier to see.
To upgrade the ground and starter wires I had new ones made up by http://www.motolectric.com/products/hicap.detail.html.
The new wires are made with very fine stranded copper that is much more flexible and of a larger diameter than OEM. Since the ground connection serves the entire system it should have a small benefit to everything electrical...heck, it can't hurt!