96 trx300fw owned since new. been sitting for a few years so i rebuilt carb. running great now. now it started smoking very bad at start up then taper off as it gets hot but still smokes a little. white smoke with a little black. getting a little valve chatter it sounds like. pulled the new plug with only a couple hours ride time and it is very black. compression test show 170 psi. any ideas a help, thanks