My neighbors ‘06 had the head breather bolts blocked off. It has the banjo bolts, but they’re blocked by large solid spacers.

I don’t know how long he has owned the bike or how long it was ridden like this.

He says it’s never leaked… a visual inspection doesn’t reveal any signs of gasket leaks.

What should be checked?

 

After replacing the breather outlet bolts I guess the only thing I would test is the operation of the umbrella valves inside the rocker covers. You should be able to suck outward, but not be able to blow back inward. A hose on the new breather bolts will allow you to test this.

Added: I would run the motor first before testing. There may be oil build up in the breather tract under the valves. You don't want to suck a mouthful of oil. Clear hose is always recommended.

 

It won't run for very long with the breathers blocked off.
It'll idle, but won't accelerate. Don't ask how I know.

 

Now see, that’s just what I would think! He claims it’s been running just fine. Gotta be pushing air out somewhere!

 

A picture would help but it doesn't sound like the head breathers are blocked; they just don't have hoses connected. The "spacers" just provide a space for whatever is passing through the head breathers to exit; otherwise, they would be blocked. Having said that, I would think that there should be some goop being ejected from the head breathers.

 

06s still had rubber stoppers in the oil tank.. Unless it was a Dyna.. If the breather was truly plugged, the dip stick would be a spaceX launch..