Malossi yellow center/contra spring 30%

Your transmission tuning is a big deal. If you are running a soft, or weak center spring, your transmission is changing too fast. The yellow is an awesome spring for the corsa/MHR/contessa cyl. This could be the difference of pulling wheelstands off the line, or your bike being a total dog until 15mph. I've seen it all too often. The yellow is a 30% stiffer spring, and is best for higher rpm bores. The next step up is the red 35% center spring. Keep in mind the stiffer the spring, the more you need a zx pulley. The oem S pulley can break due to the higher tension of the stiff springs.