Topic: F2 head with K Cylinders, leaking oil all around the head.

[MCRider]

I'm not following this completely so others may help. i will say PLEASE doNOT use any silicone on the interior of your engine. The forum as well as CB ownership at large, is rife with the tragic stories from the results of silicone. It hardens and bits break off and lodge themselves as an embulism in the oil passages. Most catastrophically in the head orifices that feed the cams. Top end burnups and cam breakages are not a rare result.

[Mandic]

I'm referring to the "dead" studs that don't have any part of the oil passages.  They are the unused oil return studs on the F2 setup.  They are open to external atmosphere, not oil passages.  The base gaskets SHOULD seal to the cylinder around the studs but Honda doubled up sealing with an O-Ring that I cannot get in a timely manner.  This is the only spot I'm proposing using it and am not 100% if it is anything but a bad idea.

[MCRider]

I'm referring to the "dead" studs that don't have any part of the oil passages.  They are the unused oil return studs on the F2 setup.  They are open to external atmosphere, not oil passages.  The base gaskets SHOULD seal to the cylinder around the studs but Honda doubled up sealing with an O-Ring that I cannot get in a timely manner.  This is the only spot I'm proposing using it and am not 100% if it is anything but a bad idea.

I see. That could be OK, up to you. As a victim of silicone myself, I spread the word.

[Mandic]

Fair warning is very welcome. 

This bike has been one Murphy's Law moment after another.  So anything like that does in fact make me think twice.

[Mandic]

While applying high tack to the base gasket I realized it will NOT seal against the block as I need.  So those O-Rings are a must.  Going to have to make a trip to the parts store and try like heck to find something that will in fact work.  Oh boy.

[scondon]

Stock cylinder studs are thinner than the heavy duty studs you're using. The o-rings from Honda are of a shape and thickness to fill the space between stock studs and the conical shaped cutout on the underside of the F2 cylinder block.

Is it possible that the undersize o-rings you have might be close to enough to fill this area now that you're using HD studs? If you haven't already installed your new rings then maybe a test fitting of the cylinder block could tell you more.

Also, this area doesn't require a "perfect" diameter seal. It's basically going to take whatever is around the cylinder stud and squish and deform it into the conical cutout in the cylinder block. If worry is that wet silicon can squeeze out on assembly into areas like the oil "trough" cut on the upper case, then maybe try putting a careful bead on your o-rings and let it dry overnight BEFORE installing.

Just thinking out loud  

[Mandic]

A member posted pictures of his F2 head that was just redone by Cycle-X.  With that Ken had them sleeve the head like we discussed earlier in this thread. You can see what appear to be bronze sleeves in there to close off the "open" passages around the cylinder studs.  I've noted a mild oil leak on my bike after high rpm highway runs.  I'm thinking the o-rings I used at the base of the cylinders didn't do the job.  Not certain yet though.  So I am buying another F2 cylinder head to port/polish, press in these sleeves and replace my current one with.

[Mandic]

BWJ posted these in his Project thread for his CB750F.

[brandEn]

I wonder if these sleeves eliminate the need for the o rings?

[Mandic]

I wonder that as well and sort of hope so.  I mean in reality they seal off any reason for the o-rings to be there.  If oil travels up or down the studs with those sleeves in place(as long as you have the rubber pucks in the head gasket area) it essentially creates a sealed situation like a K head has. 

I'm going to do it just because I want to gain a bit of power with some head work, and might as well do it while I have another head to do it on.

[Mandic]

Can you measure those holes though?  It may be the photo angle but it looks like they MAY have enlarged the holes then pressed in those bushings.  That would be good to know.

[brandEn]

Just measured with my micrometer and they are spot on .500"

[brandEn]

Thanks to this thread I learned I need copper washers for the 4 shorter HD studs with cap nuts and that 4 o rings are needed on the bottom of the cylinder in the beveled holes. I missed that in the parts fiche. Can't find the orings anywhere online though.

[Mandic]

Yea I used some random o-rings I had, and as I said, not certain that it worked. I have a high RPM oil leak from somewhere, can't fully locate it yet.

[brandEn]

For those that are watching this thread or for any future searches, keep an eye on my build thread because I am going to post pictures of all the seals, pins, gaskets, ect that go together for an F2/F3 top end rebuild. Just to clear up any questions or confusion mainly on my part! Thanks to this thread I realized I needed to order a couple more o-rings. Once I get all those in hand I will post tons of pictures.

[Mandic]

Awesome man, the more info out there the better.

I am linking your build thread in here again just in case you ever remove it from your signature.

http://forums.sohc4.net/index.php?topic=76757.0

[Terry in Australia]

Can you measure those holes though?  It may be the photo angle but it looks like they MAY have enlarged the holes then pressed in those bushings.  That would be good to know.

Ha ha, no "MAY" about it mate, those holes have definitely been machined out to take those sleeves, there's no way you could just press some sleeves into the OEM holes unless you wanted a wall thickness measured in thousands of an inch.

An easy fix though, if you don't intend on ever using your F2 block again, I'll do that when I install an F2 head on my RC Engineering 1060cc cylinder block. Cheers, Terry. 

[wohali]

FYI all - with those 5.5x3 O-Rings being discontinued, I'm using 2x O-Rings from a "Universal Series O-Ring Assortment" (Nitrile 70 Shore) rings. To fit the conical section, I'm using 1x 1/4" ID, 3/8" OD, 1/16" section (R-03) on the crankcase side, and 1x 5/16" ID, 7/16" OD, 1/16" section (R-04) on the cylinder side. Together the thickness is very close to 3mm, and the two compress nicely into that conical section.

Should be firing her up this weekend; will post here to confirm/deny that this seals the passage well.

Thanks for the informative thread!