Stock compression specs

[5twins]

I don't think these have any sort of PCV valve, it's just a plain vent. There's some baffle plates in there to keep oil from splashing out but no check valve of any kind.

 

[gggGary]

In the stock air cleaner any oil that gets past the breather baffles sits in a "trap", during high power operation it's sucked into the carbs and burned.

 

[scabber]

Compression tests will only tell you the compression is low. A leak down test will direct you to the reason it is low. If the person doing the test knows how to diagnose what the the leakdown test reveals.