what you have there is a aftermarket spring shim, they come in 2mm,4mm,6mm,10mm,12mm, these will allow you to raise the engagement up. The factory shims are the ones that only raise it approx. 100rpm per shim. If what you typed below is correct, you have a green-pink-green, the spring is 30/119 kg, to raise the engagment only up you will want a spring with higher first number and same finish(if your rpm is correct at wide open), Do you still have the short cover on prmary? if you do the closet spring to get you more in engagment and same shift rpm is the yamaha yellow-silver-yellow, it is 35/118 kg, you would probally need 3 stock yamah shims with this to be up a 1000rpm from where you are now. What you have to becarefull with is using too big of a shim, it will coilbind the spring, and it will just smoke the belt and probally break it, be sure to check for coilbind when using shims, and also, it will raise the shift rpm a very tad bit also by shimming the spring, its working in a shorter stroke now and will also diminish faster.