I run amsoil 20w50 in my street bikes with no issues. It has a wet clutch. My view is that if synthetic makes your clutch slip then it likely needed replacing anyway. I havent run amsoil in the trans of my K5. 10W40 at first and now ATF type F seems to be the best. Since I am cheap, I generally only run synthetic in a trans to smooth out notchy shifting. Cam.