1990-91 Jonsered 630 Chainsaw

Question

My husband has had this chainsaw for years and has never had a real problem with it. The other day it started and ran well on full throttle but then would quit and when he tried to start again it just sputtered and won't start. He worked on it for about 4 hrs checking through his checklists but to no avail. He thinks he might need a carb kit. I suggested the oil mixture could be problem but the same mixture works fine in my little Jonsered saw that he bought me last xmas. What else could be the problem? Or could it be a carb kit.?Should he possibly check the exhaust system?
My email is [e-mail]
sure would appreciate any input that help