Had that problem with a yz250 I bought last winter to fix up as a summer bike. Was using my snap on air hammer to try and get the bolt to come free. Ended up slipping and hammering my left ring finger when I was leaning on the air hammer with everything i had. Broke the corner of the last joint off ended up having surgery to fix it. 3 weeks after surgery slipped getting into my bobcat, natural instinct is to put your hand out to brace your fall... Broke the same finger same bone but opposite end. No surgery that time. By the time it was all said and don't I've got over 10 grand in this dam finger and it still don't work right and never will. Moral of the story take your time with it. Also I found after I started working on the bike again it helps to loosen all the other motor mounts on the bike.