2004 Skidoo ZX Series Service Manual, Page 388Get this manual
Section 08 TRANSMISSION Subsection 02 (DRIVE PULLEY)
GENERAL
Some drive pulley components (return spring, ramp) can be changed to improve vehicle performance in high altitude regionsA service bulletin will give information about calibration according to altitudeCAUTION: Such modifications should only be performed by experienced mechanics since they can greatly affect vehicle performanceVerify spring specifications before installationDo not only refer to the spring color codeNOTE: TRA drive pulley stands for Total Range Adjustable drive pulley
Models with TRA III and IV Secure drive pulley retainer (PN 529 035 674) over sliding half tower