Take to a tire shop with a " road force balancer " this can find and often fix issues with tires haveing bad spots in them. I had a similar issue with mine when I bought it. Both front tires although close to new were crap. One had a busted belt from hitting a pothole and the other had soft spots in the sdie wall plus was cupping both had under 1k miles. Also found a small bend in the right front rim but replacing the tires fixed the issue. Mine vibrated between 63mph-70mph. Now itw smooth as silk.