definitely over thinking this one. But on my 2016 street bob, using a SE breather. I’ve rigged up an external crankcase breather set up. My breather bolts have an opening of about 1/8”. But the opening at the very end of the bolt, on the end that screws into the cylinder head. Is a smaller diameter. Has anyone drilled this opening out to the same size as the rest of the bolt? What is the reasoning behind this opening being smaller than the rest of the opening in the bolt? I’m thinking it works in conjunction with the breather baffle, but I’m not sure.
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To keep the strength of the bolt so it doesn't snap when inserted or removed.

 

Huh?

 

Agree first sentence. Why would the manufacturer waste time and money on something for no dynamic gain. Mind if you feel the need just open it up.

 

My first response was first thing in the morning before I had my coffee.

 

I drilled mine out to .060 bigger and the side ports on the bolts I opened up also. Again you wanted use common sense when you do this. Just open them up a little bit. Be sure to deburr them and clean and blow them out thoroughly. I used a small file to get the bur on the inside.

 

wouldn't this allow more oil to pass through faster?

 

Huh...?

 

Does anyone know what the 4th hole is on the back of the K&N HD-1614 air filter (Rushmore bagger). If you have an external breather can/should you plug this ?

 

Yes.