I am new on here and have browsed some gearing posts. My daughter started racing a Jr Sprint, basically a micro sprint frame, with a Honda GX270 9hp engine on it this year. The engine shows max rpm at 5000 on dyno before losing torque. We run a #35 chain on these with a 13T front sprocket. We are both new to the sport and have fought chain issues for a while, breaking or coming off the sprocket. Pretty much have that figured out now. My question is rear sprocket gearing on clay oval tracks. The tracks we run are 1/5, 1/3, 1/4, 3/8 & 1/2 mile. Have a Hoosier 10/8/59 on rear left drive side and 10/8/61 on right rear. I also have a 63 & 64 in the trailer. We are running a 3/8 mile track this Saturday and I'm going back and forth on what rear sprocket to use. It is a banked clay track we have raced before and I had a 75T rear sprocket on it last time. I have a 77T on it now for Saturday but having second thoughts. It's hard to figure out sometimes since she is new at driving these and is just starting to run full throttle all the way around the tracks. I noticed on her GoPro video from last time at this track she was fast in the straightaways and slow coming out of the turns. She was getting loose coming out of turns until I made some adjustments with suspension. Can anyone give me a starting point with these 5 sized tracks I can start with, rear sprocket, tire sizes? We raced last Saturday on the 1/3 mile track and ran a 76T rear and was at 4870 rpms. Slow coming out of the corners, picked up speed on straightaways. Trying to find a happy medium, if there is one. I see other people changing rear sprockets and tires constantly between hot laps, heats and features and see no difference on performance with some of them. Thanks in advance for any help.