the cleanest motor ive ever took apart ran honda hp2 @ 40:1 ... i run klotz in my shee's but, castor927, golden spectro, belray,amsoil,klotz,hp2 are all exellent premix. change ur plugs and go chop it... see where ur at cause if theyre burnin' black chance's are ur fat. i've jetted a bunch of bikes runnin 927 and they burn fine, a nice perdy tan color.