Stihls are good chainsaws with a good reputation for not being that hard to start. I will venture to say you probably have a vacuum leak somewhere. If the saw has many - many hours of use on it the rings could also be worn. I have an ancient O21AV that usually starts on the 4th or 5th pull after setting for sometime. I also like to use 89 octane gasoline in all two cycle units. Stihl I think now recommends this for all it's engines.