Casey Stoner says the new chassis Honda brought to Assen in the hope of reducing its chatter problem has made the bike more difficult to handle.
Honda has been struggling to find a solution to its chatter troubles all season, and the situation became worse when Bridgestone recently introduced a new specification of tyre.
Stoner was only seventh fastest in MotoGP practice in the Netherlands on Thursday and said the change of chassis had not brought progress.
"We tried a few things with the bike but weren't really happy with them," he said. "We tested another chassis but haven't found many positives with it yet, in the morning if felt like we had slightly less chatter in the front, then this afternoon no real benefit, perhaps a little worse.
"In FP2 we couldn't get any feeling from the rear and to be honest I felt a little nervous on the bike because from the first two exits, the bike just wanted to throw me off, every time I touched the throttle the rear wanted to come around on me and I lost the front quite a few times, too many for my liking.
"Everything we're doing, trying to reduce the chatter is just making the bike difficult to ride. We're going to have to rethink things again and come out fresh tomorrow."
But despite his feelings about the new chassis, Stoner remained optimistic that he could get closer to the front.
"I'm not too worried about finding the pace, it was just a little bit disappointing this afternoon," he said.