OS 90 4S valve springs
Hello; does anyone know if I can use 91 surpass valve springs in my old FS 90? I have good compression and the valves are properly set and timed. The engine won't rev over 8000 rpm. I have an 14 x 6 Kseries MAS on a 4 star 60. Otherwise the engine runs great, nice low idle and easy starts. It used to take 5 feet to get off the ground, now it takes about 30 feet. There's no throttle restriction, it just won't rev up.