i bought a boygofast kit couple months ago, it's working fine. i bought another one last month, its also working well. the first engine has a more gracile looking head and had some weird silvery paint on it. the second was a more rectangular head with no paint.
first was adverts as an 80 2nd was as a 70, theres no discernable diff in the power between the 2. if i get another unpainted one i guess i'll go ahead and paint it to keep the whitish corrosion at bay.