The clickers being off? How about the valving? The clickers are trial and error, and watch what your son/bike are doing. Being a slower rider saves the valving change, for now. If he gets faster, it may be time. You really need a shop manual for that bike. It will go in solid detail about setting the sag, and fine tuning with the clickers. specifically for that bike, not mine, and his riding style. I have a friend who makes the jump from stock to a 10kg springs, without a valving change, he is old and slow though. You may try thicker/more oil also. I did not think 160 was that for off the 85, I was thinking 140 was what it came set for? Vintage Bob