First question I have is did you use assembly lube when installing everything, that will cause white smoke for a while until it all burns off. Blue smoke does indicate oil burning so you may have overheated the pistons as was previously stated. You may have caused even more issues due to ignorance of how long to let an air cooled engine idle without a fan, While yes the this engine does not have the umbrella valve as the breather assembly is in the case rather than in the rocker box.