KLE 500 Headache

[Youngatheart]

On 13, 15 and 16 September 2010 my KLE 500 wouldn’t start. I took into a bike shop and they discovered that there was no gap on the exhaust valves. The valves were actually under strain and popped out when the adjustors were released.
After this the bike went well. I had been advised to use some valve ease just to help remove the carbon that may have built up on the valve seats during the time that the valves were not closing.
I did this about 3 weeks ago. Then about a week ago I noticed that it would not idle again, and I gradually began having difficulty starting it.
Last Thursday I took it back to the bike shop. Again there was no gap on the exhaust valves. And again the valves sprang back when the adjustors were released. It is only 9 weeks since I last had to have them set.
The owner of the shop, who has raced bikes and has been in the business a long time, says it may be the valves that have become soft and are pulling into the head, although he says that this should not happen with the KLE 500. He knows of newer bikes doing it, but not the KLE.
I can’t afford to keep having this problem every 9 weeks.
Can someone please shed some light on what the problem could be?