My 02 RK just developed a decell yawl like wobble from about 65 or 70. It's a little disconcerting to say the least. Replaced the rear tire at 8000 the front has about 9000 on it but still looks OK. Progressive springs front and rear and the bike is not lowered. Spokes on both ends. Any ideas where to start looking? Bike only does it on decel from above 65.