Honda-SOHC

It seems there is something odd happening, It's always a concern if you can't identify what is really wrong and keep taking pot shots at it as you don't know if you've really fixed the problem.

Could be focusing on the wrong angle for a reason why, may be worth describing the logic to see if anyone can spot a prob in it.

If the cam cradle plugs are not leaking (they go into clear air and not the gasket anyway, don't they) the only scource of pressurized oil is from the O-rings protecting oil supply to the cam area, so the oil must be coming from them as a primary fault, right or wrong?

The head gasket is primarily there to seal the barrel to combustion chamber area and the rest is to take up any minor variation in the machined faces, if it was the original intention to stop pressured oil it would probably have had something like the barrel rings in copper around oil ways. Back to the O-rings?

Why don't they seal? If the O-rings were too big (total volume) they would hit the capacity of the counterbore and possibly prevent the head properly compressing the barrel rings, so leaking compression?

When the O-rings have been in a long time they look square is section showing that they've been squashed and seal against the casting.

Soooo the problem appears to be that the rings are not sealing against top / bottom faces, Why? (sounds like a corporate problem statement!! bit of blue sky, out of the box thinking there )

What affects that:-

Dimension, is it correct?
Material, some rings are noticeably harder that other (pattern? some applications would have a different material spec to this one, think it's called Sure rating) and would affect the physical sealing to the faces.

Clamping, assuming this is correct, but are you sure of your torque wrench accuracy. I've always used a small scale one for this 0-40lbs as it gives good seperation of scale and more accurate actuation at light loads. Have you got any genuine new Honda O-rings to use?

Hope this is of some use, any comments welcome.

I've Never used silicone on these engines, I think it's really good stuff in the right application but have taken too many things apart to find silicone bits all over the place and have a huge fear of getting any of it into small oil ways.

As Pete says, it may be good to check if the head is going clear down onto the barrels with no gasket first to see if you can spot anything.

I doubt if the gasket itself squashes to any degree, not at the torque used with flat surfaces. The design arrangement is almost perfect in that the head and the barrels are compressed buy the studs so you don't get any local distortion as you can with a stud screwed directly into the block (as on many cars).

Also check that the barrels have been seated completely before you place the head on as any binding here can the show at the head gasket when compression is applied during start-up.

I presume your torque pattern is as per book?

The suggestion for using blue hylomar is just the smallest amount spread as thin as poss both sides but to cover the whole area minus barrel rings as they should compress. The aim being to have ZERO loss of hylomar once clamped up.

I've never used increased torque as the studs are designed to be pulled into their elastic tolerance BUT NOt past it into stretch.

haven't looked here for a while, apologies for appearing rude.

Both K's are not running, had the K2 since late 70's and K6 since 80's. K6 I bought from a friend crash damaged and repaired it then it got used for years of commuting, stuck in snow a couple of times, got quite tatty used to be able to leave it anywhere but probably not any more. This now needs a full restoration but is still complete.

Used to build all sorts of engines for other people, and pick up on problems that were difficult to solve. Just enjoy mucking about with anything technical really.

Other bikes currently are Triumph Speed Triple 1995 (metalurgically challanged, needs new starter sprag clutch, just about the last component right inside the cases) nice bike though plus CBX 750 1984 on the road and current user, nice bike and maybe last 750-4 air cooled Honda?

Oooh that is a lot to do, don't they call that "time bankrupt" I'm just on painting the outside of the house, started a couple of years ago got halfway down then bought another bike, end of painting!

Noticed you've had a go at V8 Rovers as well, I've had that addiction, still not over it.

Pete, this is really good to see the build and that you've logged it so well for all of us to see.

Some observations that may help others, When cleaning threads in castings it's often easier to make a tool out of an allen bolt as a good quality black one is effectively forged and has a much higher torque capacity than a tap which is brittle. Particularly if you get any blast grit in the hole, the tap snags on this and will not cut it so bingo / snapped before you know it. If any interest I can post a method in tips maybe.

If a hardened tap is really stuck and inaccessible, if you can find anybody to do it then spark erosion can desolve it, (you'd normally have to be stripped down to a bare casting though as it has to be immersed in turps to carry out.

I bought a genuine snap-on six sided socket for the valve adjust caps years ago and it's never rounded any caps off, some people do these up as if they were going to lift the bike up by them not just to keep the oil in.

Same for the oil filter bolt, Honda put a small head on that one so you can't over torque it. It just needs doing up until the o-ring is squashed and you can feel that by gently twisting the housing left to right as you tighten until you feel the housing just contact the cases, Done.

It'll be good to see the F2 when It's running.

The ali bore before it gets to the seal groove is exposed to salt etc and usually corodes enough to go tight on the piston.

Can always push in with thumbs if operating correctly.

If you spray WD40 or similar around this and then move in / out it usaually gets easier, if so you've still got to take piston out and clean properly.

The groove and piston seal are sized (square in section) so that when you stop pulling the lever then the seal has the effect of withdrawing the piston slightly to stop the brake rubbing and building up heat when not applied.

After reasembly I put copper slip round this point to keep it cleaner in use. Cars and many later bikes have a much better crud seal on this area as I'm sure you're aware.

Oooooh! looks like nothing is sealing that should. Haven't got anything available to measure to help with o-rings currently.

You could try taking off gasket and leaving o-rings in place then slide head back on and feeler gauge the gap to see if they are going to be compressed or not to give you an estimate. They'd obviously have to exceed the gasket thickness to do anything.

Not worth wasting a 65 quid gasket until you can get some sort of answer on the o's i guess. have you got the old o-rings? They are usually compressed  when they come out so i'd estimate at .5mm plus gasket thickness to be effective.

What is the counterbore depth where the o-rings go?

BTW yoshi823 I like that frame mod of your ex F2 very neat piece of work.