OHC Valve Guides

Thanks Nick.  That the kind of reply I was slightly dreading! I hoped I'd be able to put a finger straight on the issue.  It goes well, but I fear the Police might take an interest one day.

Thanks for the ideas Jon. I've just been inspecting.  The rear oil feed has been opened and closed and doesn't seem to be the issue.  But the quill tip is worn back.  It's feed hole is about right..that is until  I turned the tip off! A new one is on order.

I took out the exhaust hairpins.  There's not enough play to be felt, so it's probably not exhaust valve. Didn't remove inlet springs (because the oil feed has to come off...).

I'll have to wait for the quill to arrive unless I make one...then see how it behaves. Then remove the pipes as you suggest.  If the engine is already hot, that should show up if they are to blame.

Then replace rings I suppose.

It has a 1932 engine. But lots of later mods. Hairpins, magnesium cambox  centre feed.  The quill in the picture is the same as Paul Norman sells.. or it should be!  Early features are the horizontal exit for the drive side crankcase breather. That was redirected upwards very soon, otherwise it exits into the later oil bath chaincase.  

The carb is an early TT version, which has a wider splayed inlet to suit a shorter, wider inlet trumpet.  Previous owner fitted a much longer one.

And yes..they are all a bit incontinent, but it's a bit more than usually so.  I just replaced the cambox seals, but with little improvement.

Using Morris C40 (castor based). Could or maybe should use 50?  I'll carry on using it because I don't want to take the engine apart to clean it all out to use a modern super synthetic oil.

Thanks Richard.

The original guides for the Inter and those commercially available now are all some kind of bronze.  The exhaust one is all in one with the lower valve spring retainer, but that can be replaced to match the inlet if necessary.

They do of course have oiling tubes.  Changing them will be a last resort.   First I'll see how it behaves with a new oil quill, and then perhaps re-check OHC oil pressure feed.  But that varies with engine revs, temperature etc.  I wonder if perhaps that is a sign of a pressure relief spring not working properly?  I don't yet know exactly what's inside the adjuster...

Rear barrel feed has been closed and opened half a turn or so with no obvious effect.  Perhaps the oil control piston ring might be worth changing, but rings are free to move.

The main thing is that it goes well.

An update.  Fitted new camshaft oil feed quill.  No difference whatsoever.  It's fine until the engine is properly warmed up, but smokes when pulling away from traffic lights.  Sadly, there are lots of these where I live.  Cocktail sticks in the valve guide oil feeds are the next step.

Update...smoke free at last!  The problem was (is?) excess oil draining down through the valve guide lubricator feed pipes. I added miniature valves to allow me to switch off the oiling at the roadside.  Close the valve (slot in screw across the pipe line) and the smoke vanishes.

Now of course I have to decide how much oil it needs. I can re-drill the screw with smaller hole.  It's not easy to simply turn it half off...because I can't see inside it.

Of course...for a race bike, this was irrelevant.  It's only a problem because the flow is constant, regardless of speed, so it becomes important only on tickover

I put a gauge on it and it varied from about 7 to 12psi.  I have had leaks and recently changed the seals. It's a lot better now.. but castor based oil leaves an almost permanent mess...

I've now been told that the inlet guide feed should be more constricted than the exhaust one. The tubes and gland nuts look very similar.  Next I'll have a good look at the adaptors into the cambox.  The inlet feed might have been wrong for years.

I think I might replace my valve screw with one with a much smaller hole.  That can be done by the roadside.

Thanks Jonathan. The brass adapters in the cambox look OK. Inlet is smaller  as it should be.  My guess is inlet guide might be worn. In a perfect world it would spend less time waiting at traffic lights!