I recently picked up a nice well maintained and hardly used 2007 WR450f. I noticed that the smallest baffle was still in the exhaust. I drilled out the 2 rivets holding it into place but it would not budge at all. I then decided to remove the entire baffle to try and get better leverage. In doing so all 4 allen head bolts broke off (#12 in picture below). I had soaked them with penetrating oil as they looked pretty fixed into place but that did no good. I used very little torque on the first one and used a 1/4" ratchet and it broke. I then decided to use an impact wrench thinking that the vibration would help. No luck it broke also. Same happened on bolts 3 and 4. Now my questions are - 1. Is this a common occurrence? 2. How do I fix it? Drill out the broken bolts and tap new threads or rivet the piece back on? 3. What can I do to prevent this from happening again if I use bolts? I did manage to get the small baffle out after breaking all 4 bolts. Man was it stuck in place. Did not want to come out. The bike came with an after market Pro Moto Billet insert to replace the stock one so do not even need the stock one but still have to bolt or rivet it back together. Any help or advice is welcome.