Hello, I am going to purchase this yz 400 for 500.00 dollars and because the the decompression lever is stuck I cannot kick it over. I am wondering if anyone can tell me how much a shop would charge for rebuild? I am think the valves may have been hit, I know they are a 100 bucks a piece, plus more for whatever else..any ideas? Should I talk this guy down more? Your advice is very much appreciated. I am lost on this, this would be my first 4 stroke. Thanks!