Handlebar headshake without hands
I have the following symptom. When decelerating the motorcycle and taking hands off the handlebar, when the speed drops from 70 km/h, the handlebar begins to slap strongly. The problem stops when I grab handlebar again. If take off my hands, the slapping starts again and stops below 40 km/h. I thought it was a problem of balancing the front wheel, but it's ok, tire and spokes are correct. The funny thing is if I take out the top case, where I carry about 5 kg, the problem is almost over, I only get a minimun slap. If I drive with the top case installed, the problem returns, with strongs slaps, so I can think that is an weight distribution issue. I tried increasing the shock preload aboit 5 clicks, but still continues. Front steering stem is thighten ok as factory. Over 80 km/h and below 40 km/h if I take off hands from handlebar, I have no problems.
Thanks for any suggestion.