Jaybird
I run a race Sprite and a road Sprite and have even had problems with the hardened valve seats in the racer until I started using a product called Tetraboost. I don't know if it is available in the USA , in the UK we get it mail order from Tetraboost, it contains Tetra Ethyl Lead, the real thing and since I started using it valve and guide wear have reduced dramatically. One warning, it is evil stuff, take care when handling it! Good luck.