Here we have a CTC Yamaha TY250 / 320 Twinshock Heavy Duty Linear fork spring upgrade kit to fit all years and models fitted with 34mm fork stanchions. 
This kit comprises of the following parts:
1 x Pair of CTC HD +10% Linear Fork Springs (replaces Yamaha Part Number 434-23141-00)  
1 x Pair of CTC HD +10% Damper rod rebound springs
1 x Pair of CTC Adjustable fork spring pre-loaders
These are British made linear springs that are 10% stronger than the original Yamaha springs that are no longer available.