Today while riding my engine suddenly started knocking or rattling loudly. I was able to limp it off the track but can't quite tell if the noise is coming from the top or bottom end. The engine starts and runs without a miss but has a knock or rattle that is very loud and sounds like possible piston slap. Anyone have any ideas what this may be? When I get some time I will pull the top end to look at and change the oil to see if there is any debris in the filter etc. It was running fine up until that point. I only have about 12 hours on the new top end but it has ran fine till now which makes me wonder if something happened on the bottom end. If anyone has any thoughts let me know! Thanks!