Help help, I have owned this bike for 4 years now it ran great then it went Kaput, It has now been at the bike mechanic for 3 years now he replaced all 16 valves , rings and worked over the carbs but when i was there today it starts and purrs like a kitten till it warms up then it wont restart... he has had this for 3 years and is pulling his hair out over it, my bike is his shop nightmare...Any suggestions on what to replace or anyone else have thisd issue also.. any help wfrom someone who knows this bike would be appreciated since they only made them 2 years it difficult..