Honda-SOHC

Hi and welcome to the forum.

You seem to have been quite thorough in working at any causes. It's possible that the floats are touching something inside the float chambers, are the floats all the same or are they handed to fit different carbs? if there is a difference it may be very small.

Agree that if valves will shut off fuel with light pressure then they should work ok.

If you turn the carbs upside down and blow through the supply you should be able to hear / feel if they are different with float bowls on or off.

We used to use cutting wheel on off-hand grinder to make one flute in allen bolts, then clean threads with needle file to de-burr and voila a good thread cleaning tool. And you can make most sizes cheaply, they don't need to be hardened as you are usually only cleaning something out not cutting into casting.

I know it's off topic for this forum but those P6 rovers are nice. There was a manual white one with period minilite wheels at newlands corner the other month, very nice.

I don't know if you recall but I've got an original spec blue colour 750 F2 stored at my place for a freind so if you need any details give us a shout, no dismantling though. It has a genuine Yoshimura pipe on it that looks really nice and an original standard set with it.

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.