i have a ys 91. it says ac on the engines but says fz on the box. it's about 5 years old. my problem is my carb barrel binds in transition. so i ordered an ac barrel with the rubber grommet. it was too small. so i ordered a fz barrel w/ rubber grommet. it was even smaller. i don't think my barrel is bad or warped. but it does have a couple of scares on it. i think i need the right rubber grommet. but none of the above fit. i recently got the engine overhauled from ys services. but they didn't replace this part. has anyone come across this or have any ideas