I have a 99 ktm 250exc, and it runs great, starts first or second kick when cold, and runs smooth for the most part. While riding the bike it runs nice, crisp, and smooth through the mid range and some of the bottom. The problem is, if I lug the bike really low, it makes a knocking type noise, but not really at all when it isn't lugging quite so low..I already removed the right side engine cover, and felt for any play in the main bearings and there was absolutely no play in the mains at all. Could this possibly be a big end rod knock? Or is it just a normal sound from lugging a ktm 2 stroke, as it's my first ktm 2 stroke and it's done it since I got it. Thanks.