I have a '95 Yamaha WR250 and an '86 Honda CR250, both of which are currently running on Honda HP2 synthetic oil at the recommended 32:1 ratio. Both bikes run well (and have done so for several years with no problems), but exhaust deposits on boldywork (and in silencer) are a real mess! I am seriously considering changing to a synthetic oil that specifically recommends running at about 50:1, such as Bel-Ray, Maxima 927, or Amsoil Series 2000. Aside from the necessary re-jetting, does anyone have any advice or real experience with 50:1 mixtures. Recommendations? Any comments on the Maxima 927 Castor stuff?