I just got it a couple months ago. Rode it once. After I rode it I took it off the truck when it was off and some how the timing chain snapped. Still not sure how it all happened but trying to put a new one on
So it has had 11 years of somebody wrenching on it.
Could be that some ape without a torque wrench has the bolt cranked up to 75-100-150 lbs and/or put some loktite on it. I would go after it gently with an impact. Sometimes a tightening a bolt just a little before trying to loosen it helps.
Does the cam still rotate.