Wr250r hard starting cold

Wrr with 14000mi, history 5000mi overheated do to pin hole in hose, 9000mi installed athena 290 big bore kit adjusted valves, valves in spec. But on the tight side so installed 1 size smaller shim to get on loose side of spec.at 14000mi very hard starting cold check valve exhast 1 to 2 shim sizes out of spec. Intakes 7 shim sizes out of spec. Adjust and rUn great now, thinking when over headed valves lost temper and are wearing prematurely.