Hi I have a 48cc Stihl chainsaw ms-250. The pull start on it is really hard to pull and it can't start it. It worked fine 2 weeks ago but my grandpa fidled with it (alzeimers) and now it won't work. I can make it turn but it is super hard to do. Yet I can't make it turn fast enough to start. I took the pull start of and when it is not on the crank shaft it pulls fine. So the crank shaft is messed up. What do I do!?