Personally, I don't think it has enough compression for the camshaft thats in it.
I used the following numbers (head gaskets and deck height were an assumption).
68CC Chamber
-2.5 Dome Volume
.050 Gasket thickness
4.2 Gasket Bore
4.155 Cyl Bore
.010 in the hole
4" stroke
That all comes out to 12.241:1 compression.
Thats a BIG bumpstick for that compression. Of course, that can be adjusted with cam timing, but you didn't say where the intake lobe was closing.