Get a note book and write down everything so the target is 9250. Example what you have now gearing, drivers, track width, length, skid along with wheel sizes and how many studs or picks, carburetor settings, clutches springs, weights, exhaust pipe, tachometer, temperature on engine, temperature of outside & barometer keeping notes you can look back on what you did. Any little change I use to write it down. Rotating mass is power loss.