This is my first post and question, so please be kind, I did a search on my question and found several things, still need advice, please. I've found a 450A that's in excellent showroom condition, other than the fact the gears/transmission? won't engage, is this a common problem, with a simple fix, or is it complicated and expensive, I can't fix it myself, just don't know enough about doing that. I can't give any more info, yet, I need to physically see the bike for myself and ask questions. So, at this point any advice would be appreciated. TIA