Tuning and Modifications: How to change your contra spring
Basics

1.  Let me first start with the fact that I am NOT a mechanic.  I have been working on motorcycles and scooters for a long time and know a little about what I am doing.  I simply take pictures for other people to use as a guide line to help them modify their own motors.  Any modifications you perform are done completely at your own risk and liability.

2.  Tampering with your motor in any way may void your warranty.  Make sure this is a sacrifice you are willing to make before you begin working on your own vehicle.

3.  Before you begin, make sure you have a nice clean area to work in.  A small amount of dirt can be a big problem when working on the innards of your motor.  Keep your hands, motor, and any other parts you are handling very clean.

4.  This example was performed on a 2002 Aprilia SR50 DiTech.  Almost all scooters have a very similar style transmission, clutch and contra spring, so the same steps should apply to your scooter.

5.  ALL bolts and socket head cap screws are in metric! Don't try to work on your vehicle if you don't have metric tools, you will just end up messing up the heads.

 
Start by removing the nut that holds the clutch and rear pulley assembly on.
Remove the bell housing and pull the entire assembly off the drive shaft.
Remove the main nut off the clutch assembly.  There is a specific tool available for this job, but it can be done with a pair of channel locks.  I use a pair of leather gloves to hold the pulley while I turn the nut with the channel locks.  Sometimes the nut is frozen on tightly and the channel locks need a good whack with a hammer to free the nut.

When removing the nut, be very careful because the entire assembly is spring loaded by the contra spring.  When the nut is removed, the clutch assembly will shoot off.  So be sur3e to hold it very tight while removing the nut.

Once the nut is removed, simply take the clutch assembly off, remove the spring and replace it with your new one.  Then push the clutch assembly down on the spring and start the nut onto the threads.  Be careful not to cross thread the nut when putting it back on.  After the nut is started, re-tighten the nut with the channel locks.  Then put the entire assembly back onto the drive shaft and replace the bell housing and nut.
 

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