I have read many of the reports about valve problems with the CRF250. What are the typical symptoms of valve problems? As far as I know my 250X is still working perfectly - but maybe I don't know what to look for. It still runs great, has good power, and I don't burn any oil. I had the dealer do the 20 hour service, which included adjusting the valves. Other than that, I haven't checked them. Are there other symptoms to look for?