Beetle Juice here I have a grubee 66cc engine just put it on my bike and have about 3 miles on it I am using amsoil Interceptor 20 to 1 ratio. Everytime I ride it I see oil when I stop seems as if it is coming from around the bottom front screw at the base of the cylinder I have enclose pic Is this normal to have some oil leaks and maybe that is where my bogging out may be coming from.
Did you take the engine apart, throw the gaskets away, and "improve" it by using red silicon in place of the gaskets? The clutch cover looks like it.
I don't think the fit between the castings is close enough to do that.