Topic: Remove Oil Restrictors?

[BenelliSEI]

Working on my very early S/C cyl. head. The restrictors have a single, angled hole on top. Prepping it for vapour blasting. Any tricks to remove these? Don’t want to lose them!

[Don R]

 I was thinking the oil jets are drilled and don't come off on the early head. Does it have the cam tower O rings on each end of them? I have a sandcast head that is so early it only has o rings on the feed end. 

[cfairweather]

To my knowledge, the oil orifice is on all CB750 heads.  The orifice in the K0 is like the K1.  These come out easily using a grease gun. After you get the K0/K1 style orifice out be sure to clean it carefully.  Run a carb cleaning wire through every hole, and there are many, to ensure it is completely clean.  Read Below:
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These orifices must be removed and carefully cleaned or you will risk ruining your engine when it goes back together.   This easy procedure has been tested on the early style orifice, but should work the same with the later style.  You do not need heat or a bent wire to remove them; just use the miracle of hydraulics and they will come out with no damage to the head or the orifice.  First, you need to tap the hole that is right next to the orifice.  Use a 1/8-27 size tap which is the size for most grease gun hoses.  This tap fits perfectly in the hole and you can easily create threads with no drilling. 

After you have threads, plug the bottom of that hole with a short piece of rubber hose, with a screw plugging the end of the hose, or you could use duct tape across the hole.  Make sure the head is on a flat surface to help seal the bottom of the plugged hole.  We want all the grease to be forced into the port that goes to the orifice.  Attach your grease gun to the threaded hole.  Put on your safety glasses as grease might shoot out of the orifice and squirt you in the eye.  Use rubber gloves and use your finger to close the orifice hole.  As you pump grease, it will be unable to get through the orifice hole because you have it blocked with your finger so it will have nowhere to go.  What happens is the grease pressure is evenly applied to the underside of the orifice and it will be pushed out of the hole.  It will come out slowly with each pump.
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[PeWe]

I thought the early Sandcast heads had holes only, nothing to remove.
I removed the earlier orifices in a post on this forum. Photos showed how.

Blocked the stud holes beside orifices on upper side of head.
I made threads for bolts blocking it.
Flipped head, filled the stud hole with oil,  used 9mm drill upside down that fitted exact in the hole.
 Smacked drill with a heavy hammer, out popped the orifice on other side catched by a plastic container.

[BenelliSEI]

Thanks for the detailed response. My engine is one of the first few hundred built and as Dan suggest, it doesn’t look like the later restrictions. Almost looks like an alloy plug with an angled hole drilled in it. Will try for a photo…..

[PeWe]

I had just got the hint how to do by a friend when this thread was started. I think same day or day before.
http://forums.sohc4.net/index.php/topic,175940.msg2051709.html#msg2051709

I guess it is possibe to block holes with a rubber plug and kept there by a clamp. Avoid making threads when head is an important one.

[BenelliSEI]

So on closer inspection (after a wash) this is different to any I have seen before. This is the 582nd SOHC, cb750 engine manufactured. I think Don was correct, this is just a solid plug, driven into the larger hole, then an angled hole is drilled through, into the stud passage, where the oil comes up. The hole is a straight shot. Look closely and you will see the wire sticking out of both ends. I think I will just leave it in place and make sure it is clear before final assembly?

There was no trace of any “0” rings but perhaps I will add a set? Thanks for all the suggestions.

[ekpent]

I'm also under the impression also that the early engines like yours do not have removable oil jets.

[MauiK3]

I may be imagining it but it looks like the counterbore may have some discoloration, caused by an o ring? Hard to tell.

[BenelliSEI]

I may be imagining it but it looks like the counterbore may have some discoloration, caused by an o ring? Hard to tell.

I don’t think so, but I’m going to size up a set.

[MRieck]

I thought the early Sandcast heads had holes only, nothing to remove.
I removed the earlier orifices in a post on this forum. Photos showed how.

Blocked the stud holes beside orifices on upper side of head.
I made threads for bolts blocking it.
Flipped head, filled the stud hole with oil,  used 9mm drill upside down that fitted exact in the hole.
 Smacked drill with a heavy hammer, out popped the orifice on other side catched by a plastic container.

Right....just an angle drilled hole on very early heads...not a very good set up.

[BenelliSEI]

I thought the early Sandcast heads had holes only, nothing to remove.
I removed the earlier orifices in a post on this forum. Photos showed how.

Blocked the stud holes beside orifices on upper side of head.
I made threads for bolts blocking it.
Flipped head, filled the stud hole with oil,  used 9mm drill upside down that fitted exact in the hole.
 Smacked drill with a heavy hammer, out popped the orifice on other side catched by a plastic container.

Right....just an angle drilled hole on very early heads...not a very good set up.

Mike....I think that is correct. Certainly different than all the others I’ve poked at. I ran the wire through and then blew them out with brakekleen using the little straw on the aerosol can. Will definitely do it again after it comes back from “vapour blasting” and just before final ensemble on the engine. Looked through everything I took apart and it appears there were no “0” rings, but thinking I may add a pair???

[Don R]

 Is your head machined on both ends of the cam towers or only one end? My reportedly 1000400 or earlier head has an o ring recess only on the feed (oil jet) end of each cam tower, not on the opposite end. 
 And I would add an o ring on each jet recess.

[BenelliSEI]

Don.... only the inside, where the oil comes up. The other ends are just plugged flush with what looks like an aluminum slug. I will use “0” rings.

[PeWe]

Important to not swap left and right ones.
If swapped, no oil at all to cam with friends.
Honda had a good reason to make equal cam holders with added o-ring for the outer hole oil stop.