I'm installing a pipe from a Pro MX 90 on my sons Pro Shark 90 along with re-jetting and air filter. Also going to do the clutch mods and was wondering what would be the best spring set for his riding, 1000, 1500, or 2000 RPM. He is a recreational rider, not racing, 11 years old. He is looking for harder acceleration off the line.



Thanks....