Ok so I bought this 07 crf70 for my little brother last Winter and it would always be hard to start, and when it did it would have some bluish tint to the exhaust. so I thought oil was getting into the cylinder and I replaced the rings. Now it really doesn't like to start? I have checked the timing it's spot on done a leak down on the valves there sealed, and have checked the piston rings and cylinder they all apper to be good. It just doesn't like to start and when it does start you have to have the throttle wide open to keep the bike running it bogs like hell and you put it into gear to go it hardly has any power. I have cleaned the carb several times to I'm at a loss I don't know what it could be any suggestions?