Yes, there were sometimes issues with too much oil and/or oil vapor coming out of the breather tubes on the earlier models. Some owners complained and Yamaha tried various things over the years to remedy the situation. Basically, the problem boiled down to being breather outlets that were too big. First thing they tried was to remove one of the hoses and plug it's outlet, only running one hose. You could try that to see if it helps .....
The next thing they tried was restoring the two hoses but fitting rubber reducer plugs with very small (like 1/8") holes in both outlets .....
Unfortunately you can't get those plugs anywhere.