I have a 2002 viper 8500 miles,I checked compression, pull cord side and center cylinders pump up good 90/first pull 120/2nd 130/3 134/4th clutch side cylinder goes 90,120,120,120 and maintains 120. I have seen other posts mention compression being stagger on these machines, is this normal? how much will parts cost? Should I do it myself? singed NEED KNOWLEDGE!