Topic: Cylinder head Cam oil holes-big and small?-Edit-Never Mind

[MCRider]

I am used to seeing the small oil holes that feed the two cam towers, (K0 to K2 or such) I just bought a head off of eBay, a K5 I think it was, which has noticably larger feed holes. And I was vaguely aware Honda had done this.

So the question is, does one update an old head by drilling out the holes, or leave well enough alone?

TIA

[mystic_1]

The newer heads have a pressed in "oil control orifice" where the earlier heads have only the small drilled hole.  Sounds like your eBay head is missing these.

mystic_1

[MCRider]

The newer heads have a pressed in "oil control orifice" where the earlier heads have only the small drilled hole.  Sounds like your eBay head is missing these.

mystic_1

OK I'll have to check a fiche (are they removable replaceable parts?) My ebay head was partially assembled and the oil holes still have the ORings in them. To the untrained eye, I wouldn't guess anything is missing.

In the meantime, Is the result of the "oil control orifice" a larger opening than the old style small hole?

[mystic_1]

Here's a pic of the hole, and the "oil control orifice" that goes into it:

[MCRider]

The newer heads have a pressed in "oil control orifice" where the earlier heads have only the small drilled hole.  Sounds like your eBay head is missing these.

mystic_1

OK I'll have to check a fiche (are they removable replaceable parts?) My ebay head was partially assembled and the oil holes still have the ORings in them. To the untrained eye, I wouldn't guess anything is missing.

In the meantime, Is the result of the "oil control orifice" a larger opening than the old style small hole?

Answers to my own question. Looking down into the orifice, the oil passage isn't any larger than the one in my old head. My smallest machinists drill bit wouldn't go through either one. Just a design change.

The orifices are removalbe and replaceable...at $28 each.

[MCRider]

great pictures mystic. That explains it, though the Fiche at Bike Bandit showed them but not as clearly. I definitely have the orifices. As mentioned, the net result is the smallest part of the orifice seems to be the same size as the drilled hole in the old head. The OD of the orifice allows the use of a much larger "O-ring". The ID of the orifice would slow down the speed of the oil rushing out of the little hole, it seems.