I went to look at a K1200lt this morning. It's a '99 bike with 42,000 miles on it. When the guy started it, there was quite a loud "knocking" from the engine somewhere. I've not heard anything so loud in either of my other two LT's I've owned. The guy said it had always done it and it went away when it warmed up. Is it likely to be something that I should walk away from?