290 rebuild

[pistolsrepair]

just did a rebuild on a 290, runs great, the problem is goin up or down hills it smokes it's @#$ off, pulled the vent from the valve cover thinkin was suckin oil from crankcase. not helpin, oil levels good. made shure to stagger ring gaps, did valve job with new seals. what am i missin? sittin in the shop holdin the pedal it will run perfect with no smoke. just up & down hills.