I have a xb12 and noticed steel shavings in the oil. The bike also has a lower end noise. It has a bouble knock when u rev it up and let off. I am told it is a spun rod? The kicker is that it is 15 days out of warranty. Its not looking good for me trying to get it covered under warranty so I am looking to rebuild the engine or should i just replace it? How hard is this engine to rebuild?