I'm just the opposite, my main site gets about 10 times the traffic from yahoo as it does from google.
It's the same with me, I get more traffic from yahoo than google. If you want to see some traffic from Yahoo you just have to wait a long time (build backlinks) until you get some traffic.
I thinks you should review some like a meta text of your pages that show in yahoo search. It should be attractive word.
Yahoo only accounts for a tiny % of our visitors, now Bing appears to be overtaking them. Google accounts for 90% of our visitors usually - that is why they are the best and most important.
I have good back links from yahoo bu5t traffic is very low . Its hard to understand but you have to search and rank for easily targeted keywords .
I would suggest getting an SEO expert to help you out with getting better rankings on the search engines to drive traffic to your website. My business has an SEO program, pm me for more information. Hope I helped!