Top US tuning house Pro Circuit already has go-faster bits for the 2017 Yamaha YZF250, starting with this performance valve springs and valve spring kit. All Pro Circuit performance engine products are designed for maximum performance and these new valve springs for the 2017 YZF250 allow the engine to run at high RPM without the loss of valve control. The full kit is available for £425 from Pro Circuit importers CHG Imports.