so my sister got this snowmachine the other day from criags list. i went for a spin with it. heard some bad sounds from the chain case. took a look at the dipstick and there was pieces on it. drained it and took the cover off. found out the bottom sprocket bolt was broken. i've seen this with my bro's pro x 550 happen. i'm wondering how can this be fixed. i have the tools to extract the bolt. i'm wondering how can i make it so it would last, meaning not break again. any suggestions?