The pump seal on mine leaked, too, when I got it. Flushed it, and ran with straight distilled water for 30 minutes. Reduced leak by 3/4. Flushed again and refilled with straight distilled water. After another 30 minutes run time, the leak stopped. Flushed and refilled with 50% Dexcool. It still doesn't leak even with full coolant pressure. The bike isn't really road worthy yet so I only have a few test miles on it. But, I can say for sure this process was easier and cheaper than changing the mechanical seal.
Cheers,