2008 Yamaha Raptor 250SE / 250SE2 Factory Service Manual, Page 145Get this manual
VALVES AND VALVE SPRINGS
4Install: Valve cotters NOTE: Install the valve cotters by compressing the valve spring with the valve spring compressor and the valve spring compressor attachment Valve spring compressor 90890-04019, YM-04019 Valve spring compressor attachment 90890-01243 Valve spring compressor adapter (26 mm) YM-01253-1