The units that are affected by this are the 42cc, 55cc, 75cc and 100cc. On your older design the spring and the spring seat were set apart on the motor. The new way is designed has two parts that go into a one part assy. And it will make putting it together a whole lot easier.
The new spring comes at a much higher spring rate than the other spring. It can be interchangeable if both of the springs and seats are recouped at the same time. This will have a new part number also. The older parts will still be available.
The old spring seat number 8800551. The old spring number 4350286. The new combination number is 513596.
If we can help you with this, other questions or if you would like us to repair your unit..call us at
662-871-8403 or 800-361-0068