Yeah, I have the 91 FX too and it is by no means a beast at all. I was very dissapointed by its stock power. After fitting a Tower 75 muffler and a 60L carb plus some dremelwork on the sleeve it became much more powerful, plus the Tower muffler saved 50 grams off the weight. Stock 91 FX is weighing 770 grams and an YS 110 is lighter and alot more power