Hmm, well the workshop made the guide and pressed it in for me. They are a very reputable shop and i'm certain that they have done it properly.
We re-assembled the rest of the head, valves, valve guide seals etc. We then turned the head upside down and dropped the valves into place (without fitting the valve springs) and then filled the combustion chamber with white spirits to check if there were any leaks around the valve seats. We kept using this method and lapped the valves in as necessary, until they no longer leaked. I don't think there is anything wrong with the head.
I still suspect the rings and bore though, as my oil it turning dis-coloured very quickly. There's no way that this can happen due to faulty valve guides and/or valve guide seals....
Dan.

1) how quicky does the oil discolour ?? What colour is it turning. If you mean it goes from clear - black, then thats perfectly normal.

If its throthy or white then there is a problem with contamination.

The bike air cooled so no worries with contamination there. Possibly a gasket somewhere.

If the oil smells like petrol then yes, the air/fuel misture could be getting forced through the rings into the oil bath below.

Odd with high compression though. You sure the carbs arnt overflowing into the bore ?

After only 150 miles or so the oil is filthy black. It shouldn't turn dirty that quickly...
Definately no fuel leaking through the carbs and into the bore though.

Completely ignore what colour it is. Its normal to change colour that quick REALLY !!

Smelling oil is the way. Should smell good. Not like coal or petrol.

Ok, Thanks Ted.
Will give it the 'smell test' after i get it back on the road and change it back to mineral oil.
Cheers, Dan.

Mineral oil wont do anything now (if ever. Its questionable about it helping to bed in rings)

What oil are you using and what kind of temperatures do you live in ??

ed

I've been using Shell SX4 15W 50, which is a semi-synthetic oil.
This problem reared its head about April last year where temperatures down here in South Aus were probably around the mid 20's. Temperatures then dropped down to as low as 5 deg for winter and then by the time i put the bike away and let the rego expire, the temperatures were back up around 30 degrees.
Dan