Oil in exhaust port - one side only

[pptom]

Guys, I'm pretty sure I know the answer to this, but, if there's any alternative I'd really appreciate any help:
Just about finished my XS hardtail dry build, very early on in the build I acquired an engine, po said it ran well, but you can never trust that. Anyway, I did a top end rebuild, noting that the LH cylinder (LH as you sit on the bike) did contain lots more carbon than the right, also the exhaust port was quite badly fouled. I put this down to worn stem seals and naturally replaced the lot during the rebuild, however, I did notice a bit of movement in the exhaust valve, but didn't measure it. At the time I phoned my local cylinder head specialist for a price to put in a new guide - he never got back to me and for various reasons I didn't chase him - just put the engine back together.
Build also included checking the ring gaps, which were fine and a very, very light hone of the cylinders.
I've had the engine running for a total of about 30 mins I suppose and noticed the LH cylinder is definately still burning oil. Stripped the bike today, ready for paint and when I removed the exhaust, I literally got a small dribble of oil out of the exhaust port. There's quite a bit of oil getting in there, but it doesn't seem to be getting in the combustion chamber as the piston looks as clean as when i fitted it, also the plug is quite clean and the RH port is bone dry.
Below is a pic of the port, I've already wiped most of the really wet oil out of it:

I've also included a picture of both plugs, although I don't know how much the colour of these can be relied on as the carbs haven't been set up and the RH cylinder isn't firing properly - LH plug on right

So, my best guess is that the guide is completely shot, I would also guess that a new valve is needed - does anyone have any other ideas?

 

[5twins]

Nope, I think you've pinpointed the problem. Although I've never actually measured for play in the valve/guide fit, I do check them by trying to wiggle the valve in the guide. It should be a nice slip fit with no wiggle. I guess I've been lucky so far because that's all I've found.

 

[sgallaty]

Very unscientific but if the valves move freely, and when I pull them out and cover the opening they form a vacuum while they are covered in engine oil (makes a nice pop when I pull out the valve), I consider them 'good enough'

 

[pptom]

Well, I suppose the big question is when do I do it?
By the time the bike is on the road, I'll have about 7 - 8 weeks riding weather before the bikes are off the road for the winter. I'd rather do the work in the long winter months, but, If I stick the bike together now, without doing the valve, will it be good enough to ride for the next few weeks? - don't want to be trailing plumes of blue smoke everywhere. The trouble is, I don't really know what its going to be like until I get out riding it, not run it for long enough in the garage for a proper test.
I'm drawing towards just sticking it in the frame and making the most of the rest of the summer.

 

[pptom]

Think the above port picture looks especially bad as I'd only run the engine for 20 seconds or so, didn't get enough time to burn the oil out.

 

[sgallaty]

Man you know, if it only smokes a little people will just be more convinced it's a triumph.

 

[5twins]

Maybe find a parts motor and just swap the whole head over?

 

[pptom]

Maybe find a parts motor and just swap the whole head over?

Wish I could, motors are going up in price over here. Even a tatty, rusty old bike would cost about £1200 (almost $2000)

 

[sgallaty]

If the bike doesn't smoke on that side much (like just a tiny blue haze) you're -probably- looking at worn stem seals, corroded/rusted exhaust valve bottoms (they can tear up the lower seal) In any case, this sounds like something you can get away with on the cheap.

If you had rings bad enough to put that much unburned oil in the exhaust port, you'd be blowing smoke out like an insect fogger.

At the very least, a new exhaust valve, seals and guide and the gaskets you'll replace when you remove the cylinder head and tappet cover.