Honda-SOHC

Rigwit, it must be like working on swiss watches with the bikes after things that size. At least you put your skills to good use with some fun engineering on the bikes although I guess you can go anywhere in a TBM!! 

Yep I noticed that in our family "bike" a VW diesel, it will do something like 40miles more to a tank on some brands than other low sulphur stuff and I heard that the pumps last longer with sulphur so aim to buy that and AVIA fuel I bought in france was the best for range that I've seen (apologies for off topic disesiel! discussion).

I guess this may not affect SOHC stuff so much but may impact on newer Injected bikes with pumped fuel supply.

That's a good point what can you coat it with? some older car tanks were painted on the inside so there must be something that would suit.

Can you still use the vinegar on your chips?

I read somewhere the other day about wrapping the fuel tank in foam, putting fine gravel inside then leaving to rotate while sucured in a cement mixer to clean the inside (was it on this forum). So if you add vinegar then a thorough clean! I geuss it's only like a gentle shot blast I suppose.

On another weird note. Worked with an old guy years ago who swore by chewing gum to stop a leak in rusting fuel tanks as a get you home fix and it does work!

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.