Firstly, I know it is oil burning. There is a small bit of oil sludge in the exhaust tip as well. I bought the bike a few weeks ago, only had a couple hours on a new top end. Bike has been running strong without any issues but was very loud. Last week: 1)I repacked the muffler, the packing that was in the exhaust was 2/3s gone, and I mean nonexistent/burnt out. 2) Changed the oil with Valvoline 10-40 four stroke oil (what prior owner was using) and new yamaha oil filter. I put in 1L as per the manual. (Put in quart, started bike/shut off, checked level, added splash to top off.) (1 quart container plus a splash from a second one) Started bike, let it warm up and rode it down the street with out issues. Yesterday, went trail riding, I was the back man, bike sounded great, pulled hard like usual. Once I passed my buddy, he made a comment my bike looked like a two stroke from behind. That's when I realized that when reving the bike I was making a smoke screen. After the hour drive home, pulled the bike off the truck and started it up to clear the carb, rode it down the street with no smoke issues. Bike only smoked when on the throttle, idle there was nothing, and no smoke on start up (cold or hot) and she fires up on 1 kick every time (cold or hot). I have not checked my oil level to see how much was burned, I will do that tonight or tomorrow. I have seen smoke issues like this with cars, when to much oil is in the system and it burns it out, (lots of smoke until it returns to normal levels). So, should I try riding again and see what happens? If there is to much oil in the system, I can drain some out and lower the level before I go riding again. Take the top end off and put a new head gasket/ oil seal on it? Thanks Fellas!