Yes get a set of valve seals. The ones I use look like little cups. Take the spring off of a bad one and a good one and without pulling the valve itself look at the difference in the existing seals. The bad one should be cracked or gone completely and the good one should still be holding tightly to the valve..
Then pull the valve out about 1/2 inch from it's seat and ROCK the stem in the hole.. do this to both and see if there is a noticeable difference in CLEARENCE in the two...If not then the seal is the problem...if however you have worn out the guide..ie made the hole too large.. then we need to go to the shop and get all new guides!
OR we neeed to get nother head.. Hopefully the five year old seals were not the best when new and that is the problem.
Big JIm <img src="/forums/images/graemlins/pfft.gif" alt="" />